text: /*
   * Copyright (C) 2011 Google Inc. All rights reserved.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions
   * are met:
   *
   * 1.  Redistributions of source code must retain the above copyright
   *     notice, this list of conditions and the following disclaimer.
   * 2.  Redistributions in binary form must reproduce the above copyright
   *     notice, this list of conditions and the following disclaimer in the
   *     documentation and/or other materials provided with the distribution.
   *
   * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
   * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
   * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
   * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
   * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
   * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
   * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
   * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
   * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
   * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   */
  
  // Trace events are for tracking application performance and resource usage.
  // Macros are provided to track:
  //    Begin and end of function calls
  //    Counters
  //
  // Events are issued against categories. Whereas LOG's
  // categories are statically defined, TRACE categories are created
  // implicitly with a string. For example:
  //   TRACE_EVENT_INSTANT0("MY_SUBSYSTEM", "SomeImportantEvent")
  //
  // Events can be INSTANT, or can be pairs of BEGIN and END in the same scope:
  //   TRACE_EVENT_BEGIN0("MY_SUBSYSTEM", "SomethingCostly")
  //   doSomethingCostly()
  //   TRACE_EVENT_END0("MY_SUBSYSTEM", "SomethingCostly")
  // Note: our tools can't always determine the correct BEGIN/END pairs unless
  // these are used in the same scope. Use ASYNC_BEGIN/ASYNC_END macros if you need them
  // to be in separate scopes.
  //
  // A common use case is to trace entire function scopes. This
  // issues a trace BEGIN and END automatically:
  //   void doSomethingCostly() {
  //     TRACE_EVENT0("MY_SUBSYSTEM", "doSomethingCostly");
  //     ...
  //   }
  //
  // Additional parameters can be associated with an event:
  //   void doSomethingCostly2(int howMuch) {
  //     TRACE_EVENT1("MY_SUBSYSTEM", "doSomethingCostly",
  //         "howMuch", howMuch);
  //     ...
  //   }
  //
  // The trace system will automatically add to this information the
  // current process id, thread id, and a timestamp in microseconds.
  //
  // To trace an asynchronous procedure such as an IPC send/receive, use ASYNC_BEGIN and
  // ASYNC_END:
  //   [single threaded sender code]
  //     static int send_count = 0;
  //     ++send_count;
  //     TRACE_EVENT_ASYNC_BEGIN0("ipc", "message", send_count);
  //     Send(new MyMessage(send_count));
  //   [receive code]
  //     void OnMyMessage(send_count) {
  //       TRACE_EVENT_ASYNC_END0("ipc", "message", send_count);
  //     }
  // The third parameter is a unique ID to match ASYNC_BEGIN/ASYNC_END pairs.
  // ASYNC_BEGIN and ASYNC_END can occur on any thread of any traced process. Pointers can
  // be used for the ID parameter, and they will be mangled internally so that
  // the same pointer on two different processes will not match. For example:
  //   class MyTracedClass {
  //    public:
  //     MyTracedClass() {
  //       TRACE_EVENT_ASYNC_BEGIN0("category", "MyTracedClass", this);
  //     }
  //     ~MyTracedClass() {
  //       TRACE_EVENT_ASYNC_END0("category", "MyTracedClass", this);
  //     }
  //   }
  //
  // Trace event also supports counters, which is a way to track a quantity
  // as it varies over time. Counters are created with the following macro:
  //   TRACE_COUNTER1("MY_SUBSYSTEM", "myCounter", g_myCounterValue);
  //
  // Counters are process-specific. The macro itself can be issued from any
  // thread, however.
  //
  // Sometimes, you want to track two counters at once. You can do this with two
  // counter macros:
  //   TRACE_COUNTER1("MY_SUBSYSTEM", "myCounter0", g_myCounterValue[0]);
  //   TRACE_COUNTER1("MY_SUBSYSTEM", "myCounter1", g_myCounterValue[1]);
  // Or you can do it with a combined macro:
  //   TRACE_COUNTER2("MY_SUBSYSTEM", "myCounter",
  //       "bytesPinned", g_myCounterValue[0],
  //       "bytesAllocated", g_myCounterValue[1]);
  // This indicates to the tracing UI that these counters should be displayed
  // in a single graph, as a summed area chart.
  //
  // Since counters are in a global namespace, you may want to disembiguate with a
  // unique ID, by using the TRACE_COUNTER_ID* variations.
  //
  // By default, trace collection is compiled in, but turned off at runtime.
  // Collecting trace data is the responsibility of the embedding
  // application. In Chrome's case, navigating to about:tracing will turn on
  // tracing and display data collected across all active processes.
  //
  //
  // Memory scoping note:
  // Tracing copies the pointers, not the string content, of the strings passed
  // in for category, name, and arg_names. Thus, the following code will
  // cause problems:
  //     char* str = strdup("impprtantName");
  //     TRACE_EVENT_INSTANT0("SUBSYSTEM", str);  // BAD!
  //     free(str);                   // Trace system now has dangling pointer
  //
  // To avoid this issue with the |name| and |arg_name| parameters, use the
  // TRACE_EVENT_COPY_XXX overloads of the macros at additional runtime overhead.
  // Notes: The category must always be in a long-lived char* (i.e. static const).
  //        The |arg_values|, when used, are always deep copied with the _COPY
  //        macros.
  //
  // When are string argument values copied:
  // const char* arg_values are only referenced by default:
  //     TRACE_EVENT1("category", "name",
  //                  "arg1", "literal string is only referenced");
  // Use TRACE_STR_COPY to force copying of a const char*:
  //     TRACE_EVENT1("category", "name",
  //                  "arg1", TRACE_STR_COPY("string will be copied"));
  // std::string arg_values are always copied:
  //     TRACE_EVENT1("category", "name",
  //                  "arg1", std::string("string will be copied"));
  //
  //
  // Thread Safety:
  // A thread safe singleton and mutex are used for thread safety. Category
  // enabled flags are used to limit the performance impact when the system
  // is not enabled.
  //
  // TRACE_EVENT macros first cache a pointer to a category. The categories are
  // statically allocated and safe at all times, even after exit. Fetching a
  // category is protected by the TraceLog::lock_. Multiple threads initializing
  // the static variable is safe, as they will be serialized by the lock and
  // multiple calls will return the same pointer to the category.
  //
  // Then the category_enabled flag is checked. This is a unsigned char, and
  // not intended to be multithread safe. It optimizes access to addTraceEvent
  // which is threadsafe internally via TraceLog::lock_. The enabled flag may
  // cause some threads to incorrectly call or skip calling addTraceEvent near
  // the time of the system being enabled or disabled. This is acceptable as
  // we tolerate some data loss while the system is being enabled/disabled and
  // because addTraceEvent is threadsafe internally and checks the enabled state
  // again under lock.
  //
  // Without the use of these static category pointers and enabled flags all
  // trace points would carry a significant performance cost of aquiring a lock
  // and resolving the category.
  
  #ifndef TraceEvent_h
  #define TraceEvent_h
  
  #include "platform/EventTracer.h"
  
  #include "wtf/DynamicAnnotations.h"
  #include "wtf/PassRefPtr.h"
  #include "wtf/text/CString.h"
  
  // By default, const char* argument values are assumed to have long-lived scope
  // and will not be copied. Use this macro to force a const char* to be copied.
  #define TRACE_STR_COPY(str) \
      WebCore::TraceEvent::TraceStringWithCopy(str)
  
  // By default, uint64 ID argument values are not mangled with the Process ID in
  // TRACE_EVENT_ASYNC macros. Use this macro to force Process ID mangling.
  #define TRACE_ID_MANGLE(id) \
      WebCore::TraceEvent::TraceID::ForceMangle(id)
  
  // By default, pointers are mangled with the Process ID in TRACE_EVENT_ASYNC
  // macros. Use this macro to prevent Process ID mangling.
  #define TRACE_ID_DONT_MANGLE(id) \
      WebCore::TraceEvent::TraceID::DontMangle(id)
  
  // Records a pair of begin and end events called "name" for the current
  // scope, with 0, 1 or 2 associated arguments. If the category is not
  // enabled, then this does nothing.
  // - category and name strings must have application lifetime (statics or
  //   literals). They may not include " chars.
  #define TRACE_EVENT0(category, name) \
      INTERNAL_TRACE_EVENT_ADD_SCOPED(category, name)
  #define TRACE_EVENT1(category, name, arg1_name, arg1_val) \
      INTERNAL_TRACE_EVENT_ADD_SCOPED(category, name, arg1_name, arg1_val)
  #define TRACE_EVENT2(category, name, arg1_name, arg1_val, arg2_name, arg2_val) \
      INTERNAL_TRACE_EVENT_ADD_SCOPED(category, name, arg1_name, arg1_val, \
          arg2_name, arg2_val)
  
  // Records a single event called "name" immediately, with 0, 1 or 2
  // associated arguments. If the category is not enabled, then this
  // does nothing.
  // - category and name strings must have application lifetime (statics or
  //   literals). They may not include " chars.
  #define TRACE_EVENT_INSTANT0(category, name) \
      INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_INSTANT, \
          category, name, TRACE_EVENT_FLAG_NONE)
  #define TRACE_EVENT_INSTANT1(category, name, arg1_name, arg1_val) \
      INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_INSTANT, \
          category, name, TRACE_EVENT_FLAG_NONE, arg1_name, arg1_val)
  #define TRACE_EVENT_INSTANT2(category, name, arg1_name, arg1_val, \
          arg2_name, arg2_val) \
      INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_INSTANT, \
          category, name, TRACE_EVENT_FLAG_NONE, arg1_name, arg1_val, \
          arg2_name, arg2_val)
  #define TRACE_EVENT_COPY_INSTANT0(category, name) \
      INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_INSTANT, \
          category, name, TRACE_EVENT_FLAG_COPY)
  #define TRACE_EVENT_COPY_INSTANT1(category, name, arg1_name, arg1_val) \
      INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_INSTANT, \
          category, name, TRACE_EVENT_FLAG_COPY, arg1_name, arg1_val)
  #define TRACE_EVENT_COPY_INSTANT2(category, name, arg1_name, arg1_val, \
          arg2_name, arg2_val) \
      INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_INSTANT, \
          category, name, TRACE_EVENT_FLAG_COPY, arg1_name, arg1_val, \
          arg2_name, arg2_val)
  
  // Records a single BEGIN event called "name" immediately, with 0, 1 or 2
  // associated arguments. If the category is not enabled, then this
  // does nothing.
  // - category and name strings must have application lifetime (statics or
  //   literals). They may not include " chars.
  #define TRACE_EVENT_BEGIN0(category, name) \
      INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_BEGIN, \
          category, name, TRACE_EVENT_FLAG_NONE)
  #define TRACE_EVENT_BEGIN1(category, name, arg1_name, arg1_val) \
      INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_BEGIN, \
          category, name, TRACE_EVENT_FLAG_NONE, arg1_name, arg1_val)
  #define TRACE_EVENT_BEGIN2(category, name, arg1_name, arg1_val, \
          arg2_name, arg2_val) \
      INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_BEGIN, \
          category, name, TRACE_EVENT_FLAG_NONE, arg1_name, arg1_val, \
          arg2_name, arg2_val)
  #define TRACE_EVENT_COPY_BEGIN0(category, name) \
      INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_BEGIN, \
          category, name, TRACE_EVENT_FLAG_COPY)
  #define TRACE_EVENT_COPY_BEGIN1(category, name, arg1_name, arg1_val) \
      INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_BEGIN, \
          category, name, TRACE_EVENT_FLAG_COPY, arg1_name, arg1_val)
  #define TRACE_EVENT_COPY_BEGIN2(category, name, arg1_name, arg1_val, \
          arg2_name, arg2_val) \
      INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_BEGIN, \
          category, name, TRACE_EVENT_FLAG_COPY, arg1_name, arg1_val, \
          arg2_name, arg2_val)
  
  // Records a single END event for "name" immediately. If the category
  // is not enabled, then this does nothing.
  // - category and name strings must have application lifetime (statics or
  //   literals). They may not include " chars.
  #define TRACE_EVENT_END0(category, name) \
      INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_END, \
          category, name, TRACE_EVENT_FLAG_NONE)
  #define TRACE_EVENT_END1(category, name, arg1_name, arg1_val) \
      INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_END, \
          category, name, TRACE_EVENT_FLAG_NONE, arg1_name, arg1_val)
  #define TRACE_EVENT_END2(category, name, arg1_name, arg1_val, \
          arg2_name, arg2_val) \
      INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_END, \
          category, name, TRACE_EVENT_FLAG_NONE, arg1_name, arg1_val, \
          arg2_name, arg2_val)
  #define TRACE_EVENT_COPY_END0(category, name) \
      INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_END, \
          category, name, TRACE_EVENT_FLAG_COPY)
  #define TRACE_EVENT_COPY_END1(category, name, arg1_name, arg1_val) \
      INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_END, \
          category, name, TRACE_EVENT_FLAG_COPY, arg1_name, arg1_val)
  #define TRACE_EVENT_COPY_END2(category, name, arg1_name, arg1_val, \
          arg2_name, arg2_val) \
      INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_END, \
          category, name, TRACE_EVENT_FLAG_COPY, arg1_name, arg1_val, \
          arg2_name, arg2_val)
  
  // Records the value of a counter called "name" immediately. Value
  // must be representable as a 32 bit integer.
  // - category and name strings must have application lifetime (statics or
  //   literals). They may not include " chars.
  #define TRACE_COUNTER1(category, name, value) \
      INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_COUNTER, \
          category, name, TRACE_EVENT_FLAG_NONE, \
          "value", static_cast<int>(value))
  #define TRACE_COPY_COUNTER1(category, name, value) \
      INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_COUNTER, \
          category, name, TRACE_EVENT_FLAG_COPY, \
          "value", static_cast<int>(value))
  
  // Records the values of a multi-parted counter called "name" immediately.
  // The UI will treat value1 and value2 as parts of a whole, displaying their
  // values as a stacked-bar chart.
  // - category and name strings must have application lifetime (statics or
  //   literals). They may not include " chars.
  #define TRACE_COUNTER2(category, name, value1_name, value1_val, \
          value2_name, value2_val) \
      INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_COUNTER, \
          category, name, TRACE_EVENT_FLAG_NONE, \
          value1_name, static_cast<int>(value1_val), \
          value2_name, static_cast<int>(value2_val))
  #define TRACE_COPY_COUNTER2(category, name, value1_name, value1_val, \
          value2_name, value2_val) \
      INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_COUNTER, \
          category, name, TRACE_EVENT_FLAG_COPY, \
          value1_name, static_cast<int>(value1_val), \
          value2_name, static_cast<int>(value2_val))
  
  // Records the value of a counter called "name" immediately. Value
  // must be representable as a 32 bit integer.
  // - category and name strings must have application lifetime (statics or
  //   literals). They may not include " chars.
  // - |id| is used to disambiguate counters with the same name. It must either
  //   be a pointer or an integer value up to 64 bits. If it's a pointer, the bits
  //   will be xored with a hash of the process ID so that the same pointer on
  //   two different processes will not collide.
  #define TRACE_COUNTER_ID1(category, name, id, value) \
      INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_COUNTER, \
          category, name, id, TRACE_EVENT_FLAG_NONE, \
          "value", static_cast<int>(value))
  #define TRACE_COPY_COUNTER_ID1(category, name, id, value) \
      INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_COUNTER, \
          category, name, id, TRACE_EVENT_FLAG_COPY, \
          "value", static_cast<int>(value))
  
  // Records the values of a multi-parted counter called "name" immediately.
  // The UI will treat value1 and value2 as parts of a whole, displaying their
  // values as a stacked-bar chart.
  // - category and name strings must have application lifetime (statics or
  //   literals). They may not include " chars.
  // - |id| is used to disambiguate counters with the same name. It must either
  //   be a pointer or an integer value up to 64 bits. If it's a pointer, the bits
  //   will be xored with a hash of the process ID so that the same pointer on
  //   two different processes will not collide.
  #define TRACE_COUNTER_ID2(category, name, id, value1_name, value1_val, \
          value2_name, value2_val) \
      INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_COUNTER, \
          category, name, id, TRACE_EVENT_FLAG_NONE, \
          value1_name, static_cast<int>(value1_val), \
          value2_name, static_cast<int>(value2_val))
  #define TRACE_COPY_COUNTER_ID2(category, name, id, value1_name, value1_val, \
          value2_name, value2_val) \
      INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_COUNTER, \
          category, name, id, TRACE_EVENT_FLAG_COPY, \
          value1_name, static_cast<int>(value1_val), \
          value2_name, static_cast<int>(value2_val))
  
  // Records a single ASYNC_BEGIN event called "name" immediately, with 0, 1 or 2
  // associated arguments. If the category is not enabled, then this
  // does nothing.
  // - category and name strings must have application lifetime (statics or
  //   literals). They may not include " chars.
  // - |id| is used to match the ASYNC_BEGIN event with the ASYNC_END event. ASYNC
  //   events are considered to match if their category, name and id values all
  //   match. |id| must either be a pointer or an integer value up to 64 bits. If
  //   it's a pointer, the bits will be xored with a hash of the process ID so
  //   that the same pointer on two different processes will not collide.
  //
  // An asynchronous operation can consist of multiple phases. The first phase is
  // defined by the ASYNC_BEGIN calls. Additional phases can be defined using the
  // ASYNC_STEP_INTO or ASYNC_STEP_PAST macros. The ASYNC_STEP_INTO macro will
  // annotate the block following the call. The ASYNC_STEP_PAST macro will
  // annotate the block prior to the call. Note that any particular event must use
  // only STEP_INTO or STEP_PAST macros; they can not mix and match. When the
  // operation completes, call ASYNC_END.
  //
  // An ASYNC trace typically occurs on a single thread (if not, they will only be
  // drawn on the thread defined in the ASYNC_BEGIN event), but all events in that
  // operation must use the same |name| and |id|. Each step can have its own
  #define TRACE_EVENT_ASYNC_BEGIN0(category, name, id) \
      INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_ASYNC_BEGIN, \
          category, name, id, TRACE_EVENT_FLAG_NONE)
  #define TRACE_EVENT_ASYNC_BEGIN1(category, name, id, arg1_name, arg1_val) \
      INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_ASYNC_BEGIN, \
          category, name, id, TRACE_EVENT_FLAG_NONE, arg1_name, arg1_val)
  #define TRACE_EVENT_ASYNC_BEGIN2(category, name, id, arg1_name, arg1_val, \
          arg2_name, arg2_val) \
      INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_ASYNC_BEGIN, \
          category, name, id, TRACE_EVENT_FLAG_NONE, \
          arg1_name, arg1_val, arg2_name, arg2_val)
  #define TRACE_EVENT_COPY_ASYNC_BEGIN0(category, name, id) \
      INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_ASYNC_BEGIN, \
          category, name, id, TRACE_EVENT_FLAG_COPY)
  #define TRACE_EVENT_COPY_ASYNC_BEGIN1(category, name, id, arg1_name, arg1_val) \
      INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_ASYNC_BEGIN, \
          category, name, id, TRACE_EVENT_FLAG_COPY, \
          arg1_name, arg1_val)
  #define TRACE_EVENT_COPY_ASYNC_BEGIN2(category, name, id, arg1_name, arg1_val, \
          arg2_name, arg2_val) \
      INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_ASYNC_BEGIN, \
          category, name, id, TRACE_EVENT_FLAG_COPY, \
          arg1_name, arg1_val, arg2_name, arg2_val)
  
  // Records a single ASYNC_STEP_INTO event for |step| immediately. If the
  // category is not enabled, then this does nothing. The |name| and |id| must
  // match the ASYNC_BEGIN event above. The |step| param identifies this step
  // within the async event. This should be called at the beginning of the next
  // phase of an asynchronous operation. The ASYNC_BEGIN event must not have any
  // ASYNC_STEP_PAST events.
  #define TRACE_EVENT_ASYNC_STEP_INTO0(category, name, id, step) \
      INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_ASYNC_STEP_INTO, \
          category, name, id, TRACE_EVENT_FLAG_NONE, "step", step)
  #define TRACE_EVENT_ASYNC_STEP_INTO1(category, name, id, step, \
          arg1_name, arg1_val) \
      INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_ASYNC_STEP_INTO, \
          category, name, id, TRACE_EVENT_FLAG_NONE, "step", step, \
          arg1_name, arg1_val)
  
  // Records a single ASYNC_STEP_PAST event for |step| immediately. If the
  // category is not enabled, then this does nothing. The |name| and |id| must
  // match the ASYNC_BEGIN event above. The |step| param identifies this step
  // within the async event. This should be called at the beginning of the next
  // phase of an asynchronous operation. The ASYNC_BEGIN event must not have any
  // ASYNC_STEP_INTO events.
  #define TRACE_EVENT_ASYNC_STEP_PAST0(category_group, name, id, step) \
      INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_ASYNC_STEP_PAST, \
          category_group, name, id, TRACE_EVENT_FLAG_NONE, "step", step)
  #define TRACE_EVENT_ASYNC_STEP_PAST1(category_group, name, id, step, arg1_name, arg1_val) \
      INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_ASYNC_STEP_PAST, \
          category_group, name, id, TRACE_EVENT_FLAG_NONE, "step", step, \
          arg1_name, arg1_val)
  
  // Records a single ASYNC_END event for "name" immediately. If the category
  // is not enabled, then this does nothing.
  #define TRACE_EVENT_ASYNC_END0(category, name, id) \
      INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_ASYNC_END, \
          category, name, id, TRACE_EVENT_FLAG_NONE)
  #define TRACE_EVENT_ASYNC_END1(category, name, id, arg1_name, arg1_val) \
      INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_ASYNC_END, \
          category, name, id, TRACE_EVENT_FLAG_NONE, arg1_name, arg1_val)
  #define TRACE_EVENT_ASYNC_END2(category, name, id, arg1_name, arg1_val, \
          arg2_name, arg2_val) \
      INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_ASYNC_END, \
          category, name, id, TRACE_EVENT_FLAG_NONE, \
          arg1_name, arg1_val, arg2_name, arg2_val)
  #define TRACE_EVENT_COPY_ASYNC_END0(category, name, id) \
      INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_ASYNC_END, \
          category, name, id, TRACE_EVENT_FLAG_COPY)
  #define TRACE_EVENT_COPY_ASYNC_END1(category, name, id, arg1_name, arg1_val) \
      INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_ASYNC_END, \
          category, name, id, TRACE_EVENT_FLAG_COPY, \
          arg1_name, arg1_val)
  #define TRACE_EVENT_COPY_ASYNC_END2(category, name, id, arg1_name, arg1_val, \
          arg2_name, arg2_val) \
      INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_ASYNC_END, \
          category, name, id, TRACE_EVENT_FLAG_COPY, \
          arg1_name, arg1_val, arg2_name, arg2_val)
  
  // Creates a scope of a sampling state with the given category and name (both must
  // be constant strings). These states are intended for a sampling profiler.
  // Implementation note: we store category and name together because we don't
  // want the inconsistency/expense of storing two pointers.
  // |thread_bucket| is [0..2] and is used to statically isolate samples in one
  // thread from others.
  //
  // {  // The sampling state is set within this scope.
  //    TRACE_EVENT_SAMPLING_STATE_SCOPE_FOR_BUCKET(0, "category", "name");
  //    ...;
  // }
  #define TRACE_EVENT_SCOPED_SAMPLING_STATE_FOR_BUCKET(bucket_number, category, name) \
      TraceEvent::SamplingStateScope<bucket_number> traceEventSamplingScope(category "\0" name);
  
  // Returns a current sampling state of the given bucket.
  // The format of the returned string is "category\0name".
  #define TRACE_EVENT_GET_SAMPLING_STATE_FOR_BUCKET(bucket_number) \
      TraceEvent::SamplingStateScope<bucket_number>::current()
  
  // Sets a current sampling state of the given bucket.
  // |category| and |name| have to be constant strings.
  #define TRACE_EVENT_SET_SAMPLING_STATE_FOR_BUCKET(bucket_number, category, name) \
      TraceEvent::SamplingStateScope<bucket_number>::set(category "\0" name)
  
  // Sets a current sampling state of the given bucket.
  // |categoryAndName| doesn't need to be a constant string.
  // The format of the string is "category\0name".
  #define TRACE_EVENT_SET_NONCONST_SAMPLING_STATE_FOR_BUCKET(bucket_number, categoryAndName) \
      TraceEvent::SamplingStateScope<bucket_number>::set(categoryAndName)
  
  // Syntactic sugars for the sampling tracing in the main thread.
  #define TRACE_EVENT_SCOPED_SAMPLING_STATE(category, name) \
      TRACE_EVENT_SCOPED_SAMPLING_STATE_FOR_BUCKET(0, category, name)
  #define TRACE_EVENT_GET_SAMPLING_STATE() \
      TRACE_EVENT_GET_SAMPLING_STATE_FOR_BUCKET(0)
  #define TRACE_EVENT_SET_SAMPLING_STATE(category, name) \
      TRACE_EVENT_SET_SAMPLING_STATE_FOR_BUCKET(0, category, name)
  #define TRACE_EVENT_SET_NONCONST_SAMPLING_STATE(categoryAndName) \
      TRACE_EVENT_SET_NONCONST_SAMPLING_STATE_FOR_BUCKET(0, categoryAndName)
  
  // Macros to track the life time and value of arbitrary client objects.
  // See also TraceTrackableObject.
  #define TRACE_EVENT_OBJECT_CREATED_WITH_ID(categoryGroup, name, id) \
      INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_CREATE_OBJECT, \
          categoryGroup, name, TRACE_ID_DONT_MANGLE(id), TRACE_EVENT_FLAG_NONE)
  
  #define TRACE_EVENT_OBJECT_DELETED_WITH_ID(categoryGroup, name, id) \
      INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_DELETE_OBJECT, \
          categoryGroup, name, TRACE_ID_DONT_MANGLE(id), TRACE_EVENT_FLAG_NONE)
  
  // Macro to efficiently determine if a given category group is enabled.
  #define TRACE_EVENT_CATEGORY_GROUP_ENABLED(categoryGroup, ret) \
      do { \
          INTERNAL_TRACE_EVENT_GET_CATEGORY_INFO(categoryGroup);  \
          if (INTERNAL_TRACE_EVENT_CATEGORY_GROUP_ENABLED_FOR_RECORDING_MODE()) { \
              *ret = true;                                        \
          } else {                                                \
              *ret = false;                                       \
          }                                                       \
      } while (0)
  
  // This will mark the trace event as disabled by default. The user will need
  // to explicitly enable the event.
  #define TRACE_DISABLED_BY_DEFAULT(name) "disabled-by-default-" name
  
  ////////////////////////////////////////////////////////////////////////////////
  // Implementation specific tracing API definitions.
  
  // Get a pointer to the enabled state of the given trace category. Only
  // long-lived literal strings should be given as the category name. The returned
  // pointer can be held permanently in a local static for example. If the
  // unsigned char is non-zero, tracing is enabled. If tracing is enabled,
  // TRACE_EVENT_API_ADD_TRACE_EVENT can be called. It's OK if tracing is disabled
  // between the load of the tracing state and the call to
  // TRACE_EVENT_API_ADD_TRACE_EVENT, because this flag only provides an early out
  // for best performance when tracing is disabled.
  // const unsigned char*
  //     TRACE_EVENT_API_GET_CATEGORY_ENABLED(const char* category_name)
  #define TRACE_EVENT_API_GET_CATEGORY_ENABLED \
      WebCore::EventTracer::getTraceCategoryEnabledFlag
  
  // Add a trace event to the platform tracing system.
  // WebCore::TraceEvent::TraceEventHandle TRACE_EVENT_API_ADD_TRACE_EVENT(
  //                    char phase,
  //                    const unsigned char* category_enabled,
  //                    const char* name,
  //                    unsigned long long id,
  //                    int num_args,
  //                    const char** arg_names,
  //                    const unsigned char* arg_types,
  //                    const unsigned long long* arg_values,
  //                    const RefPtr<ConvertableToTraceFormat>* convertableValues
  //                    unsigned char flags)
  #define TRACE_EVENT_API_ADD_TRACE_EVENT \
      WebCore::EventTracer::addTraceEvent
  
  // Set the duration field of a COMPLETE trace event.
  // void TRACE_EVENT_API_UPDATE_TRACE_EVENT_DURATION(
  //     WebCore::TraceEvent::TraceEventHandle handle)
  #define TRACE_EVENT_API_UPDATE_TRACE_EVENT_DURATION \
      WebCore::EventTracer::updateTraceEventDuration
  
  ////////////////////////////////////////////////////////////////////////////////
  
  // Implementation detail: trace event macros create temporary variables
  // to keep instrumentation overhead low. These macros give each temporary
  // variable a unique name based on the line number to prevent name collissions.
  #define INTERNAL_TRACE_EVENT_UID3(a, b) \
      trace_event_unique_##a##b
  #define INTERNAL_TRACE_EVENT_UID2(a, b) \
      INTERNAL_TRACE_EVENT_UID3(a, b)
  #define INTERNALTRACEEVENTUID(name_prefix) \
      INTERNAL_TRACE_EVENT_UID2(name_prefix, __LINE__)
  
  // Implementation detail: internal macro to create static category.
  // - WTF_ANNOTATE_BENIGN_RACE, see Thread Safety above.
  
  #define INTERNAL_TRACE_EVENT_GET_CATEGORY_INFO(category) \
      static const unsigned char* INTERNALTRACEEVENTUID(categoryGroupEnabled) = 0; \
      WTF_ANNOTATE_BENIGN_RACE(&INTERNALTRACEEVENTUID(categoryGroupEnabled), \
                               "trace_event category"); \
      if (!INTERNALTRACEEVENTUID(categoryGroupEnabled)) { \
          INTERNALTRACEEVENTUID(categoryGroupEnabled) = \
              TRACE_EVENT_API_GET_CATEGORY_ENABLED(category); \
      }
  
  // Implementation detail: internal macro to create static category and add
  // event if the category is enabled.
  #define INTERNAL_TRACE_EVENT_ADD(phase, category, name, flags, ...) \
      do { \
          INTERNAL_TRACE_EVENT_GET_CATEGORY_INFO(category); \
          if (INTERNAL_TRACE_EVENT_CATEGORY_GROUP_ENABLED_FOR_RECORDING_MODE()) { \
              WebCore::TraceEvent::addTraceEvent( \
                  phase, INTERNALTRACEEVENTUID(categoryGroupEnabled), name, \
                  WebCore::TraceEvent::noEventId, flags, ##__VA_ARGS__); \
          } \
      } while (0)
  
  // Implementation detail: internal macro to create static category and add begin
  // event if the category is enabled. Also adds the end event when the scope
  // ends.
  #define INTERNAL_TRACE_EVENT_ADD_SCOPED(category, name, ...) \
      INTERNAL_TRACE_EVENT_GET_CATEGORY_INFO(category); \
      WebCore::TraceEvent::ScopedTracer INTERNALTRACEEVENTUID(scopedTracer); \
      if (INTERNAL_TRACE_EVENT_CATEGORY_GROUP_ENABLED_FOR_RECORDING_MODE()) { \
          WebCore::TraceEvent::TraceEventHandle h = \
              WebCore::TraceEvent::addTraceEvent( \
                  TRACE_EVENT_PHASE_COMPLETE, \
                  INTERNALTRACEEVENTUID(categoryGroupEnabled), \
                  name, WebCore::TraceEvent::noEventId, \
                  TRACE_EVENT_FLAG_NONE, ##__VA_ARGS__); \
          INTERNALTRACEEVENTUID(scopedTracer).initialize( \
              INTERNALTRACEEVENTUID(categoryGroupEnabled), name, h); \
      }
  
  // Implementation detail: internal macro to create static category and add
  // event if the category is enabled.
  #define INTERNAL_TRACE_EVENT_ADD_WITH_ID(phase, category, name, id, flags, \
                                           ...) \
      do { \
          INTERNAL_TRACE_EVENT_GET_CATEGORY_INFO(category); \
          if (INTERNAL_TRACE_EVENT_CATEGORY_GROUP_ENABLED_FOR_RECORDING_MODE()) { \
              unsigned char traceEventFlags = flags | TRACE_EVENT_FLAG_HAS_ID; \
              WebCore::TraceEvent::TraceID traceEventTraceID( \
                  id, &traceEventFlags); \
              WebCore::TraceEvent::addTraceEvent( \
                  phase, INTERNALTRACEEVENTUID(categoryGroupEnabled), \
                  name, traceEventTraceID.data(), traceEventFlags, \
                  ##__VA_ARGS__); \
          } \
      } while (0)
  
  // Notes regarding the following definitions:
  // New values can be added and propagated to third party libraries, but existing
  // definitions must never be changed, because third party libraries may use old
  // definitions.
  
  // Phase indicates the nature of an event entry. E.g. part of a begin/end pair.
  #define TRACE_EVENT_PHASE_BEGIN    ('B')
  #define TRACE_EVENT_PHASE_END      ('E')
  #define TRACE_EVENT_PHASE_COMPLETE ('X')
  // FIXME: unify instant events handling between blink and platform.
  #define TRACE_EVENT_PHASE_INSTANT  ('I')
  #define TRACE_EVENT_PHASE_INSTANT_WITH_SCOPE  ('i')
  #define TRACE_EVENT_PHASE_ASYNC_BEGIN ('S')
  #define TRACE_EVENT_PHASE_ASYNC_STEP_INTO  ('T')
  #define TRACE_EVENT_PHASE_ASYNC_STEP_PAST  ('p')
  #define TRACE_EVENT_PHASE_ASYNC_END   ('F')
  #define TRACE_EVENT_PHASE_METADATA ('M')
  #define TRACE_EVENT_PHASE_COUNTER  ('C')
  #define TRACE_EVENT_PHASE_SAMPLE  ('P')
  #define TRACE_EVENT_PHASE_CREATE_OBJECT ('N')
  #define TRACE_EVENT_PHASE_DELETE_OBJECT ('D')
  
  // Flags for changing the behavior of TRACE_EVENT_API_ADD_TRACE_EVENT.
  #define TRACE_EVENT_FLAG_NONE        (static_cast<unsigned char>(0))
  #define TRACE_EVENT_FLAG_COPY        (static_cast<unsigned char>(1 << 0))
  #define TRACE_EVENT_FLAG_HAS_ID      (static_cast<unsigned char>(1 << 1))
  #define TRACE_EVENT_FLAG_MANGLE_ID   (static_cast<unsigned char>(1 << 2))
  
  // Type values for identifying types in the TraceValue union.
  #define TRACE_VALUE_TYPE_BOOL         (static_cast<unsigned char>(1))
  #define TRACE_VALUE_TYPE_UINT         (static_cast<unsigned char>(2))
  #define TRACE_VALUE_TYPE_INT          (static_cast<unsigned char>(3))
  #define TRACE_VALUE_TYPE_DOUBLE       (static_cast<unsigned char>(4))
  #define TRACE_VALUE_TYPE_POINTER      (static_cast<unsigned char>(5))
  #define TRACE_VALUE_TYPE_STRING       (static_cast<unsigned char>(6))
  #define TRACE_VALUE_TYPE_COPY_STRING  (static_cast<unsigned char>(7))
  #define TRACE_VALUE_TYPE_CONVERTABLE  (static_cast<unsigned char>(8))
  
  // These values must be in sync with base::debug::TraceLog::CategoryGroupEnabledFlags.
  #define ENABLED_FOR_RECORDING (1 << 0)
  #define ENABLED_FOR_EVENT_CALLBACK (1 << 2)
  
  #define INTERNAL_TRACE_EVENT_CATEGORY_GROUP_ENABLED_FOR_RECORDING_MODE() \
      (*INTERNALTRACEEVENTUID(categoryGroupEnabled) & (ENABLED_FOR_RECORDING | ENABLED_FOR_EVENT_CALLBACK))
  
  namespace WebCore {
  
  namespace TraceEvent {
  
  // Specify these values when the corresponding argument of addTraceEvent is not
  // used.
  const int zeroNumArgs = 0;
  const unsigned long long noEventId = 0;
  
  // TraceID encapsulates an ID that can either be an integer or pointer. Pointers
  // are mangled with the Process ID so that they are unlikely to collide when the
  // same pointer is used on different processes.
  class TraceID {
  public:
      template<bool dummyMangle> class MangleBehavior {
      public:
          template<typename T> explicit MangleBehavior(T id) : m_data(reinterpret_cast<unsigned long long>(id)) { }
          unsigned long long data() const { return m_data; }
      private:
          unsigned long long m_data;
      };
      typedef MangleBehavior<false> DontMangle;
      typedef MangleBehavior<true> ForceMangle;
  
      TraceID(const void* id, unsigned char* flags) :
          m_data(static_cast<unsigned long long>(reinterpret_cast<unsigned long>(id)))
      {
          *flags |= TRACE_EVENT_FLAG_MANGLE_ID;
      }
      TraceID(ForceMangle id, unsigned char* flags) : m_data(id.data())
      {
          *flags |= TRACE_EVENT_FLAG_MANGLE_ID;
      }
      TraceID(DontMangle id, unsigned char*) : m_data(id.data()) { }
      TraceID(unsigned long long id, unsigned char*) : m_data(id) { }
      TraceID(unsigned long id, unsigned char*) : m_data(id) { }
      TraceID(unsigned id, unsigned char*) : m_data(id) { }
      TraceID(unsigned short id, unsigned char*) : m_data(id) { }
      TraceID(unsigned char id, unsigned char*) : m_data(id) { }
      TraceID(long long id, unsigned char*) :
          m_data(static_cast<unsigned long long>(id)) { }
      TraceID(long id, unsigned char*) :
          m_data(static_cast<unsigned long long>(id)) { }
      TraceID(int id, unsigned char*) :
          m_data(static_cast<unsigned long long>(id)) { }
      TraceID(short id, unsigned char*) :
          m_data(static_cast<unsigned long long>(id)) { }
      TraceID(signed char id, unsigned char*) :
          m_data(static_cast<unsigned long long>(id)) { }
  
      unsigned long long data() const { return m_data; }
  
  private:
      unsigned long long m_data;
  };
  
  // Simple union to store various types as unsigned long long.
  union TraceValueUnion {
      bool m_bool;
      unsigned long long m_uint;
      long long m_int;
      double m_double;
      const void* m_pointer;
      const char* m_string;
  };
  
  // Simple container for const char* that should be copied instead of retained.
  class TraceStringWithCopy {
  public:
      explicit TraceStringWithCopy(const char* str) : m_str(str) { }
      const char* str() const { return m_str; }
  private:
      const char* m_str;
  };
  
  // Define setTraceValue for each allowed type. It stores the type and
  // value in the return arguments. This allows this API to avoid declaring any
  // structures so that it is portable to third_party libraries.
  #define INTERNAL_DECLARE_SET_TRACE_VALUE(actualType, argExpression, unionMember, valueTypeId) \
      static inline void setTraceValue(actualType arg, unsigned char* type, unsigned long long* value) { \
          TraceValueUnion typeValue; \
          typeValue.unionMember = argExpression; \
          *type = valueTypeId; \
          *value = typeValue.m_uint; \
      }
  // Simpler form for int types that can be safely casted.
  #define INTERNAL_DECLARE_SET_TRACE_VALUE_INT(actualType, valueTypeId) \
      static inline void setTraceValue(actualType arg, \
                                       unsigned char* type, \
                                       unsigned long long* value) { \
          *type = valueTypeId; \
          *value = static_cast<unsigned long long>(arg); \
      }
  
  INTERNAL_DECLARE_SET_TRACE_VALUE_INT(unsigned long long, TRACE_VALUE_TYPE_UINT)
  INTERNAL_DECLARE_SET_TRACE_VALUE_INT(unsigned, TRACE_VALUE_TYPE_UINT)
  INTERNAL_DECLARE_SET_TRACE_VALUE_INT(unsigned short, TRACE_VALUE_TYPE_UINT)
  INTERNAL_DECLARE_SET_TRACE_VALUE_INT(unsigned char, TRACE_VALUE_TYPE_UINT)
  INTERNAL_DECLARE_SET_TRACE_VALUE_INT(long long, TRACE_VALUE_TYPE_INT)
  INTERNAL_DECLARE_SET_TRACE_VALUE_INT(int, TRACE_VALUE_TYPE_INT)
  INTERNAL_DECLARE_SET_TRACE_VALUE_INT(short, TRACE_VALUE_TYPE_INT)
  INTERNAL_DECLARE_SET_TRACE_VALUE_INT(signed char, TRACE_VALUE_TYPE_INT)
  INTERNAL_DECLARE_SET_TRACE_VALUE(bool, arg, m_bool, TRACE_VALUE_TYPE_BOOL)
  INTERNAL_DECLARE_SET_TRACE_VALUE(double, arg, m_double, TRACE_VALUE_TYPE_DOUBLE)
  INTERNAL_DECLARE_SET_TRACE_VALUE(const void*, arg, m_pointer, TRACE_VALUE_TYPE_POINTER)
  INTERNAL_DECLARE_SET_TRACE_VALUE(const char*, arg, m_string, TRACE_VALUE_TYPE_STRING)
  INTERNAL_DECLARE_SET_TRACE_VALUE(const TraceStringWithCopy&, arg.str(), m_string, TRACE_VALUE_TYPE_COPY_STRING)
  
  #undef INTERNAL_DECLARE_SET_TRACE_VALUE
  #undef INTERNAL_DECLARE_SET_TRACE_VALUE_INT
  
  // WTF::String version of setTraceValue so that trace arguments can be strings.
  static inline void setTraceValue(const WTF::CString& arg, unsigned char* type, unsigned long long* value)
  {
      TraceValueUnion typeValue;
      typeValue.m_string = arg.data();
      *type = TRACE_VALUE_TYPE_COPY_STRING;
      *value = typeValue.m_uint;
  }
  
  static inline void setTraceValue(ConvertableToTraceFormat*, unsigned char* type, unsigned long long*)
  {
      *type = TRACE_VALUE_TYPE_CONVERTABLE;
  }
  
  template<typename T> static inline void setTraceValue(const PassRefPtr<T>& ptr, unsigned char* type, unsigned long long* value)
  {
      setTraceValue(ptr.get(), type, value);
  }
  
  template<typename T> struct ConvertableToTraceFormatTraits {
      static const bool isConvertable = false;
      static void assignIfConvertable(ConvertableToTraceFormat*& left, const T&)
      {
          left = 0;
      }
  };
  
  template<typename T> struct ConvertableToTraceFormatTraits<T*> {
      static const bool isConvertable = WTF::IsSubclass<T, TraceEvent::ConvertableToTraceFormat>::value;
      static void assignIfConvertable(ConvertableToTraceFormat*& left, ...)
      {
          left = 0;
      }
      static void assignIfConvertable(ConvertableToTraceFormat*& left, ConvertableToTraceFormat* const& right)
      {
          left = right;
      }
  };
  
  template<typename T> struct ConvertableToTraceFormatTraits<PassRefPtr<T> > {
      static const bool isConvertable = WTF::IsSubclass<T, TraceEvent::ConvertableToTraceFormat>::value;
      static void assignIfConvertable(ConvertableToTraceFormat*& left, const PassRefPtr<T>& right)
      {
          ConvertableToTraceFormatTraits<T*>::assignIfConvertable(left, right.get());
      }
  };
  
  template<typename T> bool isConvertableToTraceFormat(const T&)
  {
      return ConvertableToTraceFormatTraits<T>::isConvertable;
  }
  
  template<typename T> void assignIfConvertableToTraceFormat(ConvertableToTraceFormat*& left, const T& right)
  {
      ConvertableToTraceFormatTraits<T>::assignIfConvertable(left, right);
  }
  
  // These addTraceEvent template functions are defined here instead of in the
  // macro, because the arg values could be temporary string objects. In order to
  // store pointers to the internal c_str and pass through to the tracing API, the
  // arg values must live throughout these procedures.
  
  static inline TraceEventHandle addTraceEvent(
      char phase,
      const unsigned char* categoryEnabled,
      const char* name,
      unsigned long long id,
      unsigned char flags)
  {
      return TRACE_EVENT_API_ADD_TRACE_EVENT(
          phase, categoryEnabled, name, id,
          zeroNumArgs, 0, 0, 0,
          flags);
  }
  
  template<typename ARG1_TYPE>
  static inline TraceEventHandle addTraceEvent(
      char phase,
      const unsigned char* categoryEnabled,
      const char* name,
      unsigned long long id,
      unsigned char flags,
      const char* arg1Name,
      const ARG1_TYPE& arg1Val)
  {
      const int numArgs = 1;
      unsigned char argTypes[1];
      unsigned long long argValues[1];
      setTraceValue(arg1Val, &argTypes[0], &argValues[0]);
      if (isConvertableToTraceFormat(arg1Val)) {
          ConvertableToTraceFormat* convertableValues[1];
          assignIfConvertableToTraceFormat(convertableValues[0], arg1Val);
          return TRACE_EVENT_API_ADD_TRACE_EVENT(
              phase, categoryEnabled, name, id,
              numArgs, &arg1Name, argTypes, argValues,
              convertableValues,
              flags);
      }
      return TRACE_EVENT_API_ADD_TRACE_EVENT(
          phase, categoryEnabled, name, id,
          numArgs, &arg1Name, argTypes, argValues,
          flags);
  }
  
  template<typename ARG1_TYPE, typename ARG2_TYPE>
  static inline TraceEventHandle addTraceEvent(
      char phase,
      const unsigned char* categoryEnabled,
      const char* name,
      unsigned long long id,
      unsigned char flags,
      const char* arg1Name,
      const ARG1_TYPE& arg1Val,
      const char* arg2Name,
      const ARG2_TYPE& arg2Val)
  {
      const int numArgs = 2;
      const char* argNames[2] = { arg1Name, arg2Name };
      unsigned char argTypes[2];
      unsigned long long argValues[2];
      setTraceValue(arg1Val, &argTypes[0], &argValues[0]);
      setTraceValue(arg2Val, &argTypes[1], &argValues[1]);
      if (isConvertableToTraceFormat(arg1Val) || isConvertableToTraceFormat(arg2Val)) {
          ConvertableToTraceFormat* convertableValues[2];
          assignIfConvertableToTraceFormat(convertableValues[0], arg1Val);
          assignIfConvertableToTraceFormat(convertableValues[1], arg2Val);
          return TRACE_EVENT_API_ADD_TRACE_EVENT(
              phase, categoryEnabled, name, id,
              numArgs, argNames, argTypes, argValues,
              convertableValues,
              flags);
      }
      return TRACE_EVENT_API_ADD_TRACE_EVENT(
          phase, categoryEnabled, name, id,
          numArgs, argNames, argTypes, argValues,
          flags);
  }
  
  // Used by TRACE_EVENTx macro. Do not use directly.
  class ScopedTracer {
  public:
      // Note: members of m_data intentionally left uninitialized. See initialize.
      ScopedTracer() : m_pdata(0) { }
      ~ScopedTracer()
      {
          if (m_pdata && *m_pdata->categoryGroupEnabled)
              TRACE_EVENT_API_UPDATE_TRACE_EVENT_DURATION(m_data.categoryGroupEnabled, m_data.name, m_data.eventHandle);
      }
  
      void initialize(const unsigned char* categoryGroupEnabled, const char* name, TraceEventHandle eventHandle)
      {
          m_data.categoryGroupEnabled = categoryGroupEnabled;
          m_data.name = name;
          m_data.eventHandle = eventHandle;
          m_pdata = &m_data;
      }
  
  private:
      // This Data struct workaround is to avoid initializing all the members
      // in Data during construction of this object, since this object is always
      // constructed, even when tracing is disabled. If the members of Data were
      // members of this class instead, compiler warnings occur about potential
      // uninitialized accesses.
      struct Data {
          const unsigned char* categoryGroupEnabled;
          const char* name;
          TraceEventHandle eventHandle;
      };
      Data* m_pdata;
      Data m_data;
  };
  
  // TraceEventSamplingStateScope records the current sampling state
  // and sets a new sampling state. When the scope exists, it restores
  // the sampling state having recorded.
  template<size_t BucketNumber>
  class SamplingStateScope {
      WTF_MAKE_FAST_ALLOCATED;
  public:
      SamplingStateScope(const char* categoryAndName)
      {
          m_previousState = SamplingStateScope<BucketNumber>::current();
          SamplingStateScope<BucketNumber>::set(categoryAndName);
      }
  
      ~SamplingStateScope()
      {
          SamplingStateScope<BucketNumber>::set(m_previousState);
      }
  
      // FIXME: Make load/store to traceSamplingState[] thread-safe and atomic.
      static inline const char* current()
      {
          return reinterpret_cast<const char*>(*WebCore::traceSamplingState[BucketNumber]);
      }
      static inline void set(const char* categoryAndName)
      {
          *WebCore::traceSamplingState[BucketNumber] = reinterpret_cast<long>(const_cast<char*>(categoryAndName));
      }
  
  private:
      const char* m_previousState;
  };
  
  template<typename IDType> class TraceScopedTrackableObject {
      WTF_MAKE_NONCOPYABLE(TraceScopedTrackableObject);
  public:
      TraceScopedTrackableObject(const char* categoryGroup, const char* name, IDType id)
          : m_categoryGroup(categoryGroup), m_name(name), m_id(id)
      {
          TRACE_EVENT_OBJECT_CREATED_WITH_ID(m_categoryGroup, m_name, m_id);
      }
  
      ~TraceScopedTrackableObject()
      {
          TRACE_EVENT_OBJECT_DELETED_WITH_ID(m_categoryGroup, m_name, m_id);
      }
  
  private:
      const char* m_categoryGroup;
      const char* m_name;
      IDType m_id;
  };
  
  } // namespace TraceEvent
  
  } // namespace WebCore
  
  #endif
  