text: // Copyright (c) 2012 The Chromium Authors. All rights reserved.
  // Use of this source code is governed by a BSD-style license that can be
  // found in the LICENSE file.
  
  #include "content/browser/histogram_message_filter.h"
  
  #include "base/command_line.h"
  #include "base/metrics/histogram.h"
  #include "base/metrics/statistics_recorder.h"
  #include "content/browser/histogram_controller.h"
  #include "content/browser/tcmalloc_internals_request_job.h"
  #include "content/common/child_process_messages.h"
  #include "content/public/common/content_switches.h"
  
  namespace content {
  
  HistogramMessageFilter::HistogramMessageFilter() {}
  
  void HistogramMessageFilter::OnChannelConnected(int32 peer_pid) {
    BrowserMessageFilter::OnChannelConnected(peer_pid);
  }
  
  bool HistogramMessageFilter::OnMessageReceived(const IPC::Message& message,
                                                bool* message_was_ok) {
    bool handled = true;
    IPC_BEGIN_MESSAGE_MAP_EX(HistogramMessageFilter, message, *message_was_ok)
      IPC_MESSAGE_HANDLER(ChildProcessHostMsg_ChildHistogramData,
                          OnChildHistogramData)
      IPC_MESSAGE_HANDLER(ChildProcessHostMsg_GetBrowserHistogram,
                          OnGetBrowserHistogram)
      IPC_MESSAGE_UNHANDLED(handled = false)
    IPC_END_MESSAGE_MAP_EX()
    return handled;
  }
  
  HistogramMessageFilter::~HistogramMessageFilter() {}
  
  void HistogramMessageFilter::OnChildHistogramData(
      int sequence_number,
      const std::vector<std::string>& pickled_histograms) {
    HistogramController::GetInstance()->OnHistogramDataCollected(
        sequence_number, pickled_histograms);
  }
  
  void HistogramMessageFilter::OnGetBrowserHistogram(
      const std::string& name,
      std::string* histogram_json) {
    DCHECK(content::BrowserThread::CurrentlyOn(content::BrowserThread::IO));
    // Security: Only allow access to browser histograms when running in the
    // context of a test.
    bool using_stats_collection_controller =
        CommandLine::ForCurrentProcess()->HasSwitch(
            switches::kStatsCollectionController);
    if (!using_stats_collection_controller) {
      LOG(ERROR) << "Attempt at reading browser histogram without specifying "
                 << "--" << switches::kStatsCollectionController << " switch.";
      return;
    }
    base::HistogramBase* histogram =
        base::StatisticsRecorder::FindHistogram(name);
    if (!histogram) {
      *histogram_json = "{}";
    } else {
      histogram->WriteJSON(histogram_json);
    }
  }
  
  }  // namespace content
  