Wrap MediaMetadata in base::Optional in content and chrome

content/renderer/media/android/renderer_media_session_manager.h

Index: content/renderer/media/android/renderer_media_session_manager.h
diff --git a/content/renderer/media/android/renderer_media_session_manager.h b/content/renderer/media/android/renderer_media_session_manager.h
index fbfd5c848b057fd027094c836f0634c8748acfca..9f0bd7ab7168ddece1e54fed451ad05864035a3d 100644
--- a/content/renderer/media/android/renderer_media_session_manager.h
+++ b/content/renderer/media/android/renderer_media_session_manager.h
@@ -14,6 +14,10 @@
 #include "content/public/renderer/render_frame_observer.h"
 #include "third_party/WebKit/public/platform/modules/mediasession/WebMediaSession.h"
 
+namespace base {
+template <typename T> class Optional;

[dcheng, 2016/09/06 21:11:16]

Let's just #include base/optional.h. One day this is going to be the C++
standard optional, and the forward declare will horribly explode. The same is
true for all other forward declarations.

[Zhiqiang Zhang (Slow), 2016/09/07 10:45:06]

Done.

+}  // namespace base
+
 namespace content {
 
 class WebMediaSessionAndroid;
@@ -36,7 +40,8 @@ class CONTENT_EXPORT RendererMediaSessionManager : public RenderFrameObserver {
   void Deactivate(
       int session_id,
       std::unique_ptr<blink::WebMediaSessionDeactivateCallback> callback);
-  void SetMetadata(int session_id, const MediaMetadata& metadata);
+  void SetMetadata(
+      int session_id, const base::Optional<MediaMetadata>& metadata);
 
   void OnDidActivate(int request_id, bool success);
   void OnDidDeactivate(int request_id);