Add ability to retrieve capabilities for audio input devices to MediaDevicesDispatcherHost.

content/browser/renderer_host/media/media_stream_manager.cc

Index: content/browser/renderer_host/media/media_stream_manager.cc
diff --git a/content/browser/renderer_host/media/media_stream_manager.cc b/content/browser/renderer_host/media/media_stream_manager.cc
index 5818cef620e58357d7f789e52d61c7e64d4cb19e..9437850fa45e7dbf5057d30f19bd4874ae25cb75 100644
--- a/content/browser/renderer_host/media/media_stream_manager.cc
+++ b/content/browser/renderer_host/media/media_stream_manager.cc
@@ -463,6 +463,11 @@ MediaDevicesManager* MediaStreamManager::media_devices_manager() {
   return media_devices_manager_.get();
 }
 
+media::AudioSystem* MediaStreamManager::audio_system() {
+  DCHECK_CURRENTLY_ON(BrowserThread::IO);
+  return audio_system_;
+}
+
 void MediaStreamManager::AddVideoCaptureObserver(
     media::VideoCaptureObserver* capture_observer) {
   DCHECK_CURRENTLY_ON(BrowserThread::IO);