Crash fix: Remove MessageLoop from AudioPowerMonitor and instead use MessageLoopProxy in AudioOutpu…

media/audio/audio_output_controller.cc

 // 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 "media/audio/audio_output_controller.h"
 
 #include "base/bind.h"
 #include "base/debug/trace_event.h"
 #include "base/message_loop/message_loop.h"
 #include "base/metrics/histogram.h"
 #include "base/threading/platform_thread.h"
 #include "base/time/time.h"
 #include "build/build_config.h"
-#include "media/audio/audio_power_monitor.h"
 #include "media/audio/audio_util.h"
 #include "media/audio/shared_memory_util.h"
 #include "media/base/scoped_histogram_timer.h"
 
 using base::Time;
 using base::TimeDelta;
 
 namespace media {
 
 // Time constant for AudioPowerMonitor.  See AudioPowerMonitor ctor comments for
@@ skipping 17 matching lines @@
       params_(params),
       handler_(handler),
       input_device_id_(input_device_id),
       stream_(NULL),
       diverting_to_stream_(NULL),
       volume_(1.0),
       state_(kEmpty),
       num_allowed_io_(0),
       sync_reader_(sync_reader),
       message_loop_(audio_manager->GetMessageLoop()),
-      number_polling_attempts_left_(0) {
+      number_polling_attempts_left_(0),
+      power_monitor_(
+          params.sample_rate(),
+          TimeDelta::FromMilliseconds(kPowerMeasurementTimeConstantMillis)) {
   DCHECK(audio_manager);
   DCHECK(handler_);
   DCHECK(sync_reader_);
   DCHECK(message_loop_.get());
 }
 
 AudioOutputController::~AudioOutputController() {
   DCHECK_EQ(kClosed, state_);
 }
 
@@ skipping 86 matching lines @@
 
   // We can start from created or paused state.
   if (state_ != kCreated && state_ != kPaused)
     return;
 
   // Ask for first packet.
   sync_reader_->UpdatePendingBytes(0);
 
   state_ = kPlaying;
 
-  // Start monitoring power levels and send an initial notification that we're
-  // starting in silence.
-  handler_->OnPowerMeasured(AudioPowerMonitor::zero_power(), false);
-  power_monitor_callback_.Reset(
-      base::Bind(&EventHandler::OnPowerMeasured, base::Unretained(handler_)));
-  power_monitor_.reset(new AudioPowerMonitor(
-      params_.sample_rate(),
-      TimeDelta::FromMilliseconds(kPowerMeasurementTimeConstantMillis),
-      TimeDelta::FromSeconds(1) / kPowerMeasurementsPerSecond,
-      base::MessageLoop::current(),
-      power_monitor_callback_.callback()));
+  power_monitor_.Reset();
+  power_poll_callback_.Reset(
+      base::Bind(&AudioOutputController::ReportPowerMeasurementPeriodically,
+                 this));
+  // Run the callback to send an initial notification that we're starting in
+  // silence, and to schedule periodic callbacks.
+  power_poll_callback_.callback().Run();
 
   // We start the AudioOutputStream lazily.
   AllowEntryToOnMoreIOData();
   stream_->Start(this);
 
   handler_->OnPlaying();
 }
 
+void AudioOutputController::ReportPowerMeasurementPeriodically() {
+  DCHECK(message_loop_->BelongsToCurrentThread());
+  const std::pair<float, bool>& reading =
+      power_monitor_.ReadCurrentPowerAndClip();
+  handler_->OnPowerMeasured(reading.first, reading.second);
+  message_loop_->PostDelayedTask(
+      FROM_HERE, power_poll_callback_.callback(),
+      TimeDelta::FromSeconds(1) / kPowerMeasurementsPerSecond);
+}
+
 void AudioOutputController::StopStream() {
   DCHECK(message_loop_->BelongsToCurrentThread());
 
   if (state_ == kPlaying) {
     stream_->Stop();
     DisallowEntryToOnMoreIOData();
 
-    // Stop monitoring power levels.  By canceling power_monitor_callback_, any
-    // tasks posted to |message_loop_| by AudioPowerMonitor during the
-    // stream_->Stop() call above will not run.
-    power_monitor_.reset();
-    power_monitor_callback_.Cancel();
+    power_poll_callback_.Cancel();
 
     state_ = kPaused;
   }
 }
 
 void AudioOutputController::DoPause() {
   DCHECK(message_loop_->BelongsToCurrentThread());
   SCOPED_UMA_HISTOGRAM_TIMER("Media.AudioOutputController.PauseTime");
 
   StopStream();
@@ skipping 72 matching lines @@
     const bool kShouldBlock = true;
 #else
     const bool kShouldBlock = diverting_to_stream_ != NULL;
 #endif
 
   const int frames = sync_reader_->Read(kShouldBlock, source, dest);
   DCHECK_LE(0, frames);
   sync_reader_->UpdatePendingBytes(
       buffers_state.total_bytes() + frames * params_.GetBytesPerFrame());
 
-  power_monitor_->Scan(*dest, frames);
+  power_monitor_.Scan(*dest, frames);
 
   AllowEntryToOnMoreIOData();
   return frames;
 }
 
 void AudioOutputController::OnError(AudioOutputStream* stream) {
   // Handle error on the audio controller thread.
   message_loop_->PostTask(FROM_HERE, base::Bind(
       &AudioOutputController::DoReportError, this));
 }
@@ skipping 93 matching lines @@
   DCHECK(base::AtomicRefCountIsZero(&num_allowed_io_));
   base::AtomicRefCountInc(&num_allowed_io_);
 }
 
 void AudioOutputController::DisallowEntryToOnMoreIOData() {
   const bool is_zero = !base::AtomicRefCountDec(&num_allowed_io_);
   DCHECK(is_zero);
 }
 
 }  // namespace media