Added volume adjust sound behind the flag.

media/audio/sounds/audio_stream_handler.cc

Index: media/audio/sounds/audio_stream_handler.cc
diff --git a/media/audio/sounds/audio_stream_handler.cc b/media/audio/sounds/audio_stream_handler.cc
index 49709769f7c54fde19caabc05c1afc303cf1886d..f28635645a4873d51fc72f32f661e3716e7dfbe0 100644
--- a/media/audio/sounds/audio_stream_handler.cc
+++ b/media/audio/sounds/audio_stream_handler.cc
@@ -6,8 +6,11 @@
 
 #include <string>
 
+#include "base/cancelable_callback.h"
 #include "base/logging.h"
 #include "base/single_thread_task_runner.h"
+#include "base/synchronization/lock.h"
+#include "base/time/time.h"
 #include "media/audio/audio_manager.h"
 #include "media/audio/audio_manager_base.h"
 #include "media/base/channel_layout.h"
@@ -22,6 +25,9 @@ const double kOutputVolumePercent = 0.8;
 // The number of frames each OnMoreData() call will request.
 const int kDefaultFrameCount = 1024;
 
+// Keep alive timeout for audio stream.
+const int kKeepAliveMs = 1500;
+
 AudioStreamHandler::TestObserver* g_observer_for_testing = NULL;
 AudioOutputStream::AudioSourceCallback* g_audio_source_for_testing = NULL;
 
@@ -30,12 +36,12 @@ AudioOutputStream::AudioSourceCallback* g_audio_source_for_testing = NULL;
 class AudioStreamHandler::AudioStreamContainer
     : public AudioOutputStream::AudioSourceCallback {
  public:
-  AudioStreamContainer(const WavAudioHandler& wav_audio,
-                       const AudioParameters& params)
+  AudioStreamContainer(const WavAudioHandler& wav_audio)
       : stream_(NULL),
         wav_audio_(wav_audio),
-        params_(params),
-        cursor_(0) {
+        cursor_(0),
+        started_(false),
+        delayed_stop_posted_(false) {
   }
 
   virtual ~AudioStreamContainer() {
@@ -46,20 +52,38 @@ class AudioStreamHandler::AudioStreamContainer
     DCHECK(AudioManager::Get()->GetTaskRunner()->BelongsToCurrentThread());
 
     if (!stream_) {
-      stream_ = AudioManager::Get()->MakeAudioOutputStreamProxy(params_,
-                                                                std::string(),
-                                                                std::string());
+      const AudioParameters& p = wav_audio_.params();
+      const AudioParameters params(AudioParameters::AUDIO_PCM_LOW_LATENCY,
+                                   p.channel_layout(),
+                                   p.sample_rate(),
+                                   p.bits_per_sample(),
+                                   kDefaultFrameCount);
+      stream_ = AudioManager::Get()->MakeAudioOutputStreamProxy(
+          params, std::string(), std::string());
       if (!stream_ || !stream_->Open()) {
         LOG(ERROR) << "Failed to open an output stream.";
         return;
       }
       stream_->SetVolume(kOutputVolumePercent);
-    } else {
-      // TODO (ygorshenin@): implement smart stream rewind.
-      stream_->Stop();
     }
 
-    cursor_ = 0;
+    {
+      base::AutoLock al(state_lock_);
+
+      delayed_stop_posted_ = false;
+      stop_closure_.Reset(base::Bind(
+          &AudioStreamContainer::StopStream, base::Unretained(this)));
+
+      if (started_) {
+        if (wav_audio_.AtEnd(cursor_))
+          cursor_ = 0;
+        return;
+      }
+
+      cursor_ = 0;
+      started_ = true;
+    }
+
     if (g_audio_source_for_testing)
       stream_->Start(g_audio_source_for_testing);
     else
@@ -71,14 +95,10 @@ class AudioStreamHandler::AudioStreamContainer
 
   void Stop() {
     DCHECK(AudioManager::Get()->GetTaskRunner()->BelongsToCurrentThread());
-    if (!stream_)
-      return;
-    stream_->Stop();
-    stream_->Close();
+    StopStream();
+    if (stream_)
+      stream_->Close();
     stream_ = NULL;
-
-    if (g_observer_for_testing)
-      g_observer_for_testing->OnStop(cursor_);
   }
 
  private:
@@ -86,16 +106,21 @@ class AudioStreamHandler::AudioStreamContainer
   // Following methods could be called from *ANY* thread.
   virtual int OnMoreData(AudioBus* dest,
                          AudioBuffersState /* state */) OVERRIDE {
+    base::AutoLock al(state_lock_);
     size_t bytes_written = 0;
+
     if (wav_audio_.AtEnd(cursor_) ||
         !wav_audio_.CopyTo(dest, cursor_, &bytes_written)) {
-      AudioManager::Get()->GetTaskRunner()->PostTask(
+      if (delayed_stop_posted_)
+        return 0;
+      delayed_stop_posted_ = true;
+      AudioManager::Get()->GetTaskRunner()->PostDelayedTask(
           FROM_HERE,
-          base::Bind(&AudioStreamContainer::Stop, base::Unretained(this)));
+          stop_closure_.callback(),
+          base::TimeDelta::FromMilliseconds(kKeepAliveMs));
       return 0;
     }
     cursor_ += bytes_written;
-
     return dest->frames();
   }
 
@@ -109,12 +134,28 @@ class AudioStreamHandler::AudioStreamContainer
     LOG(ERROR) << "Error during system sound reproduction.";
   }
 
+  void StopStream() {
+    DCHECK(AudioManager::Get()->GetTaskRunner()->BelongsToCurrentThread());
+
+    base::AutoLock al(state_lock_);
+
+    if (stream_ && started_) {
+      stream_->Stop();
+      if (g_observer_for_testing)
+        g_observer_for_testing->OnStop(cursor_);
+    }
+    started_ = false;
+  }
+
   AudioOutputStream* stream_;
 
   const WavAudioHandler wav_audio_;
-  const AudioParameters params_;
 
+  base::Lock state_lock_;
   size_t cursor_;
+  bool started_;
+  bool delayed_stop_posted_;
+  base::CancelableClosure stop_closure_;
 
   DISALLOW_COPY_AND_ASSIGN(AudioStreamContainer);
 };
@@ -127,16 +168,11 @@ AudioStreamHandler::AudioStreamHandler(const base::StringPiece& wav_data)
     LOG(ERROR) << "Can't get access to audio manager.";
     return;
   }
-  AudioParameters params(AudioParameters::AUDIO_PCM_LOW_LATENCY,
-                         GuessChannelLayout(wav_audio_.num_channels()),
-                         wav_audio_.sample_rate(),
-                         wav_audio_.bits_per_sample(),
-                         kDefaultFrameCount);
-  if (!params.IsValid()) {
+  if (!wav_audio_.params().IsValid()) {
     LOG(ERROR) << "Audio params are invalid.";
     return;
   }
-  stream_.reset(new AudioStreamContainer(wav_audio_, params));
+  stream_.reset(new AudioStreamContainer(wav_audio_));
   initialized_ = true;
 }
 
@@ -146,7 +182,7 @@ AudioStreamHandler::~AudioStreamHandler() {
       FROM_HERE,
       base::Bind(&AudioStreamContainer::Stop, base::Unretained(stream_.get())));
   AudioManager::Get()->GetTaskRunner()->DeleteSoon(FROM_HERE,
-                                                    stream_.release());
+                                                   stream_.release());
 }
 
 bool AudioStreamHandler::IsInitialized() const {