Add thread safety to AudioManagerBase to protect access to the audio thread member variable.

media/audio/audio_output_proxy.cc

Index: media/audio/audio_output_proxy.cc
diff --git a/media/audio/audio_output_proxy.cc b/media/audio/audio_output_proxy.cc
index e8309cf372dda72417ab87add262d31a3aad8167..6d7e8782784e69ea6414020e7ebb6a6ba96196d9 100644
--- a/media/audio/audio_output_proxy.cc
+++ b/media/audio/audio_output_proxy.cc
@@ -14,17 +14,16 @@ AudioOutputProxy::AudioOutputProxy(AudioOutputDispatcher* dispatcher)
       state_(kCreated),
       physical_stream_(NULL),
       volume_(1.0) {
-  DCHECK_EQ(MessageLoop::current(), dispatcher_->message_loop());
 }
 
 AudioOutputProxy::~AudioOutputProxy() {
-  DCHECK_EQ(MessageLoop::current(), dispatcher_->message_loop());
+  DCHECK(CalledOnValidThread());
   DCHECK(state_ == kCreated || state_ == kClosed);
   DCHECK(!physical_stream_);
 }
 
 bool AudioOutputProxy::Open() {
-  DCHECK_EQ(MessageLoop::current(), dispatcher_->message_loop());
+  DCHECK(CalledOnValidThread());
   DCHECK_EQ(state_, kCreated);
 
   if (!dispatcher_->StreamOpened()) {
@@ -37,7 +36,7 @@ bool AudioOutputProxy::Open() {
 }
 
 void AudioOutputProxy::Start(AudioSourceCallback* callback) {
-  DCHECK_EQ(MessageLoop::current(), dispatcher_->message_loop());
+  DCHECK(CalledOnValidThread());
   DCHECK(physical_stream_ == NULL);
   DCHECK_EQ(state_, kOpened);
 
@@ -54,7 +53,7 @@ void AudioOutputProxy::Start(AudioSourceCallback* callback) {
 }
 
 void AudioOutputProxy::Stop() {
-  DCHECK_EQ(MessageLoop::current(), dispatcher_->message_loop());
+  DCHECK(CalledOnValidThread());
   if (state_ != kPlaying)
     return;
 
@@ -66,7 +65,7 @@ void AudioOutputProxy::Stop() {
 }
 
 void AudioOutputProxy::SetVolume(double volume) {
-  DCHECK_EQ(MessageLoop::current(), dispatcher_->message_loop());
+  DCHECK(CalledOnValidThread());
   volume_ = volume;
   if (physical_stream_) {
     physical_stream_->SetVolume(volume);
@@ -74,12 +73,12 @@ void AudioOutputProxy::SetVolume(double volume) {
 }
 
 void AudioOutputProxy::GetVolume(double* volume) {
-  DCHECK_EQ(MessageLoop::current(), dispatcher_->message_loop());
+  DCHECK(CalledOnValidThread());
   *volume = volume_;
 }
 
 void AudioOutputProxy::Close() {
-  DCHECK_EQ(MessageLoop::current(), dispatcher_->message_loop());
+  DCHECK(CalledOnValidThread());
   DCHECK(state_ == kCreated || state_ == kError || state_ == kOpened);
   DCHECK(!physical_stream_);