Add support for the audio-output-device switching IPC mechanism to the renderer lower layers (media…

media/base/audio_renderer_sink.h

Index: media/base/audio_renderer_sink.h
diff --git a/media/base/audio_renderer_sink.h b/media/base/audio_renderer_sink.h
index fa1ee84c250a10e16eb0db310b38a31cd555c65c..753135d0c261516e348098cbc147ea8cd559ff56 100644
--- a/media/base/audio_renderer_sink.h
+++ b/media/base/audio_renderer_sink.h
@@ -5,16 +5,27 @@
 #ifndef MEDIA_BASE_AUDIO_RENDERER_SINK_H_
 #define MEDIA_BASE_AUDIO_RENDERER_SINK_H_
 
+#include <string>
 #include <vector>
+
 #include "base/basictypes.h"
+#include "base/callback.h"
 #include "base/logging.h"
 #include "base/memory/ref_counted.h"
+#include "media/audio/audio_output_ipc.h"
 #include "media/audio/audio_parameters.h"
 #include "media/base/audio_bus.h"
 #include "media/base/media_export.h"
+#include "url/gurl.h"
+
+namespace base {
+class SingleThreadTaskRunner;
+}
 
 namespace media {
 
+typedef base::Callback<void(SwitchOutputDeviceResult)> SwitchOutputDeviceCB;
+
 // AudioRendererSink is an interface representing the end-point for
 // rendered audio.  An implementation is expected to
 // periodically call Render() on a callback object.
@@ -56,6 +67,21 @@ class AudioRendererSink
   // Returns |true| on success.
   virtual bool SetVolume(double volume) = 0;
 
+  // Attempts to switch the audio output device.
+  // Once the attempt is finished, |callback| is invoked with the
+  // result of the operation passed as a parameter. The result is a value from
+  // the  media::SwitchOutputDeviceResult enum.
+  // There is no guarantee about the thread where |callback| will
+  // be invoked, so users are advised to use media::BindToCurrentLoop() to
+  // ensure that |callback| runs on the correct thread.
+  // Note also that copy constructors and destructors for arguments bound to
+  // |callback| may run on arbitrary threads as |callback| is moved across
+  // threads. It is advisable to bind arguments such that they are released by
+  // |callback| when it runs in order to avoid surprises.
+  virtual void SwitchOutputDevice(const std::string& device_id,
+                                  const GURL& security_origin,
+                                  const SwitchOutputDeviceCB& callback) = 0;
+
  protected:
   friend class base::RefCountedThreadSafe<AudioRendererSink>;
   virtual ~AudioRendererSink() {}