Add support for switching the audio output device for HTMLMediaElements.

media/audio/audio_output_device.cc

Index: media/audio/audio_output_device.cc
diff --git a/media/audio/audio_output_device.cc b/media/audio/audio_output_device.cc
index 960c84b11505d7d06d1ef0083202b898d7376129..1c4c825f5d08332039e871d475d381954517130f 100644
--- a/media/audio/audio_output_device.cc
+++ b/media/audio/audio_output_device.cc
@@ -5,6 +5,7 @@
 #include "media/audio/audio_output_device.h"
 
 #include "base/basictypes.h"
+#include "base/thread_task_runner_handle.h"
 #include "base/threading/thread_restrictions.h"
 #include "base/time/time.h"
 #include "base/trace_event/trace_event.h"
@@ -46,7 +47,8 @@ AudioOutputDevice::AudioOutputDevice(
       state_(IDLE),
       play_on_start_(true),
       session_id_(-1),
-      stopping_hack_(false) {
+      stopping_hack_(false),
+      next_switch_request_id_(0) {
   CHECK(ipc_);
 
   // The correctness of the code depends on the relative values assigned in the
@@ -118,6 +120,19 @@ bool AudioOutputDevice::SetVolume(double volume) {
   return true;
 }
 
+void AudioOutputDevice::SwitchOutputDevice(
+    const std::string& device_id,
+    const GURL& security_origin,
+    const base::Callback<void(int)>& callback) {
+  DVLOG(1) << __FUNCTION__ << "(" << device_id << ")";
+  task_runner()->PostTask(FROM_HERE,
+      base::Bind(&AudioOutputDevice::SwitchOutputDeviceOnIOThread,
+                 this,
+                 device_id,
+                 security_origin,
+                 callback));
+}
+
 void AudioOutputDevice::CreateStreamOnIOThread(const AudioParameters& params) {
   DCHECK(task_runner()->BelongsToCurrentThread());
   if (state_ == IDLE) {
@@ -180,6 +195,18 @@ void AudioOutputDevice::SetVolumeOnIOThread(double volume) {
     ipc_->SetVolume(volume);
 }
 
+void AudioOutputDevice::SwitchOutputDeviceOnIOThread(
+    const std::string& device_id,
+    const GURL& security_origin,
+    const base::Callback<void(int)>& callback) {
+  DCHECK(task_runner()->BelongsToCurrentThread());
+  DVLOG(1) << __FUNCTION__ << "(" << device_id << "," << security_origin << ")";
+  if (state_ >= CREATING_STREAM) {
+    int request_id = AddSwitchRequest(callback);
+    ipc_->SwitchDevice(device_id, security_origin, request_id, callback);
+  }
+}
+
 void AudioOutputDevice::OnStateChanged(AudioOutputIPCDelegate::State state) {
   DCHECK(task_runner()->BelongsToCurrentThread());
 
@@ -256,6 +283,29 @@ void AudioOutputDevice::OnStreamCreated(
     PlayOnIOThread();
 }
 
+int AudioOutputDevice::AddSwitchRequest(
+    const base::Callback<void(int)>& callback) {
+  DCHECK(task_runner()->BelongsToCurrentThread());
+  DVLOG(1) << __PRETTY_FUNCTION__;
+  int request_id = next_switch_request_id_++;
+  switch_requests_[request_id] = callback;
+  return request_id;
+}
+
+void AudioOutputDevice::OnDeviceSwitched(
+    int request_id, AudioOutputIPCDelegate::DeviceSwitchResult result) {
+  DCHECK(task_runner()->BelongsToCurrentThread());
+  DVLOG(1) << __PRETTY_FUNCTION__
+           << "(" << request_id << ", " << result << ")";
+  auto request = switch_requests_.find(request_id);
+  if (request == switch_requests_.end()) {
+    return;
+  }
+
+  request->second.Run(result);
+  switch_requests_.erase(request);
+}
+
 void AudioOutputDevice::OnIPCClosed() {
   DCHECK(task_runner()->BelongsToCurrentThread());
   state_ = IPC_CLOSED;