Wrap MediaMetadata in base::Optional in content and chrome

content/public/browser/web_contents_observer.h

Index: content/public/browser/web_contents_observer.h
diff --git a/content/public/browser/web_contents_observer.h b/content/public/browser/web_contents_observer.h
index e2c42d0eefd9afc07bb09af1a0415f35dff06e6e..b836de0fcb6b946ee9a8c5d477282f5958954d61 100644
--- a/content/public/browser/web_contents_observer.h
+++ b/content/public/browser/web_contents_observer.h
@@ -8,6 +8,7 @@
 #include <stdint.h>
 
 #include "base/macros.h"
+#include "base/optional.h"

[mlamouri (slow - plz ping), 2016/09/01 17:47:49]

can't you forward declare `const T&`?

[Zhiqiang Zhang (Slow), 2016/09/01 18:19:37]

Sorry, I didn't quite follow here.
Do you mean forward declare base::Optional<> or content::MediaMetadata?

[Zhiqiang Zhang (Slow), 2016/09/02 12:11:41]

Done.

 #include "base/process/kill.h"
 #include "base/process/process_handle.h"
 #include "content/common/content_export.h"
@@ -469,9 +470,10 @@ class CONTENT_EXPORT WebContentsObserver : public IPC::Listener,
   virtual void MediaStoppedPlaying(const MediaPlayerId& id) {}
 
   // Invoked when media session has changed its state.
-  virtual void MediaSessionStateChanged(bool is_controllable,
-                                        bool is_suspended,
-                                        const MediaMetadata& metadata) {}
+  virtual void MediaSessionStateChanged(
+      bool is_controllable,
+      bool is_suspended,
+      const base::Optional<MediaMetadata>& metadata) {}
 
   // Invoked when the renderer process changes the page scale factor.
   virtual void OnPageScaleFactorChanged(float page_scale_factor) {}