Initialization of audio manager for Android is now done on the audio thread

media/audio/android/audio_manager_android.cc

Index: media/audio/android/audio_manager_android.cc
diff --git a/media/audio/android/audio_manager_android.cc b/media/audio/android/audio_manager_android.cc
index 33e9e085688de87c37eebfbdbfdeddfb9949f2db..24ad96882382edfe5f20a08949f5ec945f796b6d 100644
--- a/media/audio/android/audio_manager_android.cc
+++ b/media/audio/android/audio_manager_android.cc
@@ -9,6 +9,7 @@
 #include "base/android/jni_string.h"
 #include "base/android/scoped_java_ref.h"
 #include "base/logging.h"
+#include "base/message_loop/message_loop.h"
 #include "base/strings/string_number_conversions.h"
 #include "jni/AudioManagerAndroid_jni.h"
 #include "media/audio/android/audio_record_input.h"
@@ -45,9 +46,9 @@ AudioManager* CreateAudioManager(AudioLogFactory* audio_log_factory) {
 }
 
 AudioManagerAndroid::AudioManagerAndroid(AudioLogFactory* audio_log_factory)
-    : AudioManagerBase(audio_log_factory) {
+    : AudioManagerBase(audio_log_factory),
+      initialized_on_audio_thread_(false) {
   SetMaxOutputStreamsAllowed(kMaxOutputStreams);
-
   j_audio_manager_.Reset(
       Java_AudioManagerAndroid_createAudioManagerAndroid(
           base::android::AttachCurrentThread(),
@@ -59,6 +60,8 @@ AudioManagerAndroid::AudioManagerAndroid(AudioLogFactory* audio_log_factory)
 AudioManagerAndroid::~AudioManagerAndroid() {
   Close();
   Shutdown();
+  // Verify that WillDestroyCurrentMessageLoop() has been called.
+  DCHECK(!initialized_on_audio_thread_);
 }
 
 bool AudioManagerAndroid::HasAudioOutputDevices() {
@@ -71,26 +74,22 @@ bool AudioManagerAndroid::HasAudioInputDevices() {
 
 void AudioManagerAndroid::GetAudioInputDeviceNames(
     AudioDeviceNames* device_names) {
-  // Always add default device parameters as first element.
-  DCHECK(device_names->empty());
-  AddDefaultDevice(device_names);
-
-  JNIEnv* env = AttachCurrentThread();
-  ScopedJavaLocalRef<jobjectArray> j_device_array =
-      Java_AudioManagerAndroid_getAudioInputDeviceNames(
-          env, j_audio_manager_.obj());
-  jsize len = env->GetArrayLength(j_device_array.obj());
-  AudioDeviceName device;
-  for (jsize i = 0; i < len; ++i) {
-    ScopedJavaLocalRef<jobject> j_device(
-        env, env->GetObjectArrayElement(j_device_array.obj(), i));
-    ScopedJavaLocalRef<jstring> j_device_name =
-        Java_AudioDeviceName_name(env, j_device.obj());
-    ConvertJavaStringToUTF8(env, j_device_name.obj(), &device.device_name);
-    ScopedJavaLocalRef<jstring> j_device_id =
-        Java_AudioDeviceName_id(env, j_device.obj());
-    ConvertJavaStringToUTF8(env, j_device_id.obj(), &device.unique_id);
-    device_names->push_back(device);
+  // Get list of available audio devices and use the audio thread to reduce
+  // the number of calling threads to the Java layer. Also, ensure that the
+  // calling thread sees this function call as synchronous.
+  scoped_refptr<base::SingleThreadTaskRunner> task_runner(GetTaskRunner());
+  if (task_runner->BelongsToCurrentThread()) {
+    GetAudioInputDeviceNamesOnAudioThread(NULL, device_names);
+  } else {
+    base::WaitableEvent event(false, false);
+    task_runner->PostTask(
+        FROM_HERE,
+        base::Bind(
+            &AudioManagerAndroid::GetAudioInputDeviceNamesOnAudioThread,
+            base::Unretained(this),
+            &event,
+            device_names));
+    event.Wait();
   }
 }
 
@@ -146,6 +145,7 @@ AudioOutputStream* AudioManagerAndroid::MakeAudioOutputStream(
 
 AudioInputStream* AudioManagerAndroid::MakeAudioInputStream(
     const AudioParameters& params, const std::string& device_id) {
+  DCHECK(GetTaskRunner()->BelongsToCurrentThread());
   bool had_no_streams = HadNoAudioStreams();
   AudioInputStream* stream =
       AudioManagerBase::MakeAudioInputStream(params, device_id);
@@ -206,6 +206,7 @@ AudioInputStream* AudioManagerAndroid::MakeLinearInputStream(
 AudioInputStream* AudioManagerAndroid::MakeLowLatencyInputStream(
     const AudioParameters& params, const std::string& device_id) {
   DCHECK_EQ(AudioParameters::AUDIO_PCM_LOW_LATENCY, params.format());
+  DCHECK(GetTaskRunner()->BelongsToCurrentThread());
   DLOG_IF(ERROR, device_id.empty()) << "Invalid device ID!";
   // Use the device ID to select the correct input device.
   // Note that the input device is always associated with a certain output
@@ -232,6 +233,13 @@ AudioInputStream* AudioManagerAndroid::MakeLowLatencyInputStream(
   return new OpenSLESInputStream(this, params);
 }
 
+void AudioManagerAndroid::WillDestroyCurrentMessageLoop() {
+  // This call matches previous calls to InitializeOnAudioThread() and it
+  // ensures that we unregister receivers for events related to changes in
+  // availability of audio devices.
+  CloseOnAudioThread();
+}
+
 int AudioManagerAndroid::GetOptimalOutputFrameSize(int sample_rate,
                                                    int channels) {
   if (IsAudioLowLatencySupported()) {
@@ -303,26 +311,75 @@ void AudioManagerAndroid::SetMute(JNIEnv* env, jobject obj, jboolean muted) {
           muted));
 }
 
-void AudioManagerAndroid::DoSetMuteOnAudioThread(bool muted) {
-  base::AutoLock lock(streams_lock_);
-  for (OutputStreams::iterator it = streams_.begin();
-       it != streams_.end(); ++it) {
-    (*it)->SetMute(muted);
+void AudioManagerAndroid::GetAudioInputDeviceNamesOnAudioThread(
+    base::WaitableEvent* event, AudioDeviceNames* device_names) {
+  DCHECK(GetTaskRunner()->BelongsToCurrentThread());
+
+  // Set up the initial list of available audio devices and register for
+  // broadcasted notifications about any changes of availability.
+  // This method is only executed when called for the first time and it can
+  // also be called from SetAudioDeviceOnAudioThread().
+  InitializeOnAudioThread();
+
+  // Always add default device parameters as first element.
+  DCHECK(device_names->empty());
+  AddDefaultDevice(device_names);
+
+  JNIEnv* env = AttachCurrentThread();
+  ScopedJavaLocalRef<jobjectArray> j_device_array =
+      Java_AudioManagerAndroid_getAudioInputDeviceNames(
+          env, j_audio_manager_.obj());
+  jsize len = env->GetArrayLength(j_device_array.obj());
+  AudioDeviceName device;
+  for (jsize i = 0; i < len; ++i) {
+    ScopedJavaLocalRef<jobject> j_device(
+        env, env->GetObjectArrayElement(j_device_array.obj(), i));
+    ScopedJavaLocalRef<jstring> j_device_name =
+        Java_AudioDeviceName_name(env, j_device.obj());
+    ConvertJavaStringToUTF8(env, j_device_name.obj(), &device.device_name);
+    ScopedJavaLocalRef<jstring> j_device_id =
+        Java_AudioDeviceName_id(env, j_device.obj());
+    ConvertJavaStringToUTF8(env, j_device_id.obj(), &device.unique_id);
+    device_names->push_back(device);
   }
+
+  if (event)
+    event->Signal();
 }
 
-void AudioManagerAndroid::SetCommunicationAudioModeOn(bool on) {
-  Java_AudioManagerAndroid_setCommunicationAudioModeOn(
-      base::android::AttachCurrentThread(),
-      j_audio_manager_.obj(), on);
+void AudioManagerAndroid::InitializeOnAudioThread() {
+  DCHECK(GetTaskRunner()->BelongsToCurrentThread());
+  if (!initialized_on_audio_thread_) {
+    base::MessageLoop::current()->AddDestructionObserver(this);
+    Java_AudioManagerAndroid_initAudioDeviceList(
+        base::android::AttachCurrentThread(),
+        j_audio_manager_.obj());
+    initialized_on_audio_thread_ = true;
+  }
+}
+
+void AudioManagerAndroid::CloseOnAudioThread() {
+  DCHECK(GetTaskRunner()->BelongsToCurrentThread());
+  if (!initialized_on_audio_thread_)
+    return;
+  Java_AudioManagerAndroid_closeAudioDeviceList(
+        base::android::AttachCurrentThread(),
+        j_audio_manager_.obj());
+  initialized_on_audio_thread_ = false;
 }
 
 bool AudioManagerAndroid::SetAudioDevice(const std::string& device_id) {
-  JNIEnv* env = AttachCurrentThread();
+  DCHECK(GetTaskRunner()->BelongsToCurrentThread());
+  // Set up the initial list of available audio devices and register for
+  // broadcasted notifications about any changes of availability.
+  // This method is only executed when called for the first time and it can
+  // also be called from GetAudioInputDeviceNamesOnAudioThread().
+  InitializeOnAudioThread();
 
   // Send the unique device ID to the Java audio manager and make the
   // device switch. Provide an empty string to the Java audio manager
   // if the default device is selected.
+  JNIEnv* env = AttachCurrentThread();
   ScopedJavaLocalRef<jstring> j_device_id = ConvertUTF8ToJavaString(
       env,
       device_id == AudioManagerBase::kDefaultDeviceId ?
@@ -331,6 +388,21 @@ bool AudioManagerAndroid::SetAudioDevice(const std::string& device_id) {
       env, j_audio_manager_.obj(), j_device_id.obj());
 }
 
+void AudioManagerAndroid::DoSetMuteOnAudioThread(bool muted) {
+  DCHECK(GetTaskRunner()->BelongsToCurrentThread());
+  base::AutoLock lock(streams_lock_);
+  for (OutputStreams::iterator it = streams_.begin();
+       it != streams_.end(); ++it) {
+    (*it)->SetMute(muted);
+  }
+}
+
+void AudioManagerAndroid::SetCommunicationAudioModeOn(bool on) {
+  Java_AudioManagerAndroid_setCommunicationAudioModeOn(
+      base::android::AttachCurrentThread(),
+      j_audio_manager_.obj(), on);
+}
+
 int AudioManagerAndroid::GetNativeOutputSampleRate() {
   return Java_AudioManagerAndroid_getNativeOutputSampleRate(
       base::android::AttachCurrentThread(),