Wrap MediaMetadata in base::Optional in content and chrome

content/renderer/media/android/renderer_media_session_manager.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CONTENT_RENDERER_MEDIA_ANDROID_RENDERER_MEDIA_SESSION_MANAGER_H_
 #define CONTENT_RENDERER_MEDIA_ANDROID_RENDERER_MEDIA_SESSION_MANAGER_H_
 
 #include <map>
 #include <memory>
 
 #include "base/id_map.h"
 #include "base/macros.h"
 #include "content/common/content_export.h"
 #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;
 struct MediaMetadata;
 
 class CONTENT_EXPORT RendererMediaSessionManager : public RenderFrameObserver {
  public:
   RendererMediaSessionManager(RenderFrame* render_frame);
   ~RendererMediaSessionManager() override;
 
   // RenderFrameObserver override.
   bool OnMessageReceived(const IPC::Message& msg) override;
 
   int RegisterMediaSession(WebMediaSessionAndroid* session);
   void UnregisterMediaSession(int session_id);
 
   void Activate(
       int session_id,
       std::unique_ptr<blink::WebMediaSessionActivateCallback> callback);
   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);
 
  private:
   friend class WebMediaSessionTest;
 
   // RenderFrameObserver implementation.
   void OnDestruct() override;
 
   std::map<int, WebMediaSessionAndroid*> sessions_;
   int next_session_id_;
 
   using ActivationRequests =
       IDMap<blink::WebMediaSessionActivateCallback, IDMapOwnPointer>;
   ActivationRequests pending_activation_requests_;
 
   using DeactivationRequests =
       IDMap<blink::WebMediaSessionDeactivateCallback, IDMapOwnPointer>;
   DeactivationRequests pending_deactivation_requests_;
 
   DISALLOW_COPY_AND_ASSIGN(RendererMediaSessionManager);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_MEDIA_ANDROID_RENDERER_MEDIA_SESSION_MANAGER_H_