Add support for switching the audio output device for HTMLMediaElements.

media/audio/null_audio_sink.cc

Index: media/audio/null_audio_sink.cc
diff --git a/media/audio/null_audio_sink.cc b/media/audio/null_audio_sink.cc
index e737c437c9c8d47a2af1ae90a805cfa1f49bb4ba..c15356971303a6fcf780a0820e9b10247c38397a 100644
--- a/media/audio/null_audio_sink.cc
+++ b/media/audio/null_audio_sink.cc
@@ -70,6 +70,14 @@ bool NullAudioSink::SetVolume(double volume) {
   return volume == 0.0;
 }
 
+void NullAudioSink::SwitchOutputDevice(
+    const std::string &device_id,
+    const GURL& security_origin,
+    const base::Callback<void(int)>& callback) {
+  DCHECK(task_runner_->BelongsToCurrentThread());
+}

[miu, 2015/06/03 21:01:01]

ditto: Run callback.  Maybe the NullAudioSink should just "fake out" a success
code here?

+
+
 void NullAudioSink::CallRender() {
   DCHECK(task_runner_->BelongsToCurrentThread());