Allow MessageFilters to restrict listening to specific message classes

content/browser/renderer_host/media/audio_renderer_host.cc

Index: content/browser/renderer_host/media/audio_renderer_host.cc
diff --git a/content/browser/renderer_host/media/audio_renderer_host.cc b/content/browser/renderer_host/media/audio_renderer_host.cc
index 165989e58e56e0d6caa7ce13e86afff04918b213..9cc0e11d767a64d122ca169e040aa3fb23d0c8ad 100644
--- a/content/browser/renderer_host/media/audio_renderer_host.cc
+++ b/content/browser/renderer_host/media/audio_renderer_host.cc
@@ -27,6 +27,11 @@ using media::AudioBus;
 using media::AudioManager;
 
 namespace content {
+namespace {
+const uint32 kFilteredMessageClasses[] = {
+  AudioMsgStart
+};
+}  // namespace
 
 class AudioRendererHost::AudioEntry
     : public media::AudioOutputController::EventHandler {
@@ -114,7 +119,9 @@ AudioRendererHost::AudioRendererHost(
     AudioMirroringManager* mirroring_manager,
     MediaInternals* media_internals,
     MediaStreamManager* media_stream_manager)
-    : render_process_id_(render_process_id),
+    : BrowserMessageFilter(
+          kFilteredMessageClasses, arraysize(kFilteredMessageClasses)),
+      render_process_id_(render_process_id),
       audio_manager_(audio_manager),
       mirroring_manager_(mirroring_manager),
       audio_log_(media_internals->CreateAudioLog(