Add groupid for media devices. Group audio devices.

content/public/common/media_stream_request.h

Index: content/public/common/media_stream_request.h
diff --git a/content/public/common/media_stream_request.h b/content/public/common/media_stream_request.h
index c24b1bf72a25c61babcf31941d9fc73da523c4ff..26b2bf1121b1e8d2187299305663f7876fc0047a 100644
--- a/content/public/common/media_stream_request.h
+++ b/content/public/common/media_stream_request.h
@@ -129,6 +129,11 @@ struct CONTENT_EXPORT MediaStreamDevice {
   // The device's "friendly" name. Not guaranteed to be unique.
   std::string name;
 
+  // A unique identifier for the physical device this device is part of.
+  // Will be hashed before being sent to renderer.
+  // TODO(maxmorin): Add support for video devices as well.
+  std::string group_id;
+
   // Contains properties that match directly with those with the same name
   // in media::AudioParameters.
   // TODO(ajm): Remove this type and use media::AudioParameters directly.