message: Make the call to wait_until_system_clock more explicit.
  MSVC complains about this:
  .\tensorflow/core/platform/default/mutex.h(33): error C2872: 'internal': ambiguous symbol
  .\tensorflow/core/platform/default/mutex.h(24): note: could be 'tensorflow::internal'
diff: @@ -30,7 +30,7 @@ std::cv_status wait_until_system_clock(
  template <class Rep, class Period>
  std::cv_status condition_variable::wait_for(
  mutex_lock &lock, std::chrono::duration<Rep, Period> dur) {
  - return internal::wait_until_system_clock(
  + return tensorflow::internal::wait_until_system_clock(
  &this->cv_, &lock.mutex()->mu_, std::chrono::system_clock::now() + dur);
  }
  