Implement MediaSession (metadata) per frame [NOT READY, HAS DEPENDENCY]

content/browser/web_contents/web_contents_impl.cc

Index: content/browser/web_contents/web_contents_impl.cc
diff --git a/content/browser/web_contents/web_contents_impl.cc b/content/browser/web_contents/web_contents_impl.cc
index 683bd7154d435222b2627e276aa7c6a001a10d12..f6b6997ccd30c583ec66b2b820d5db8bdfaa00f0 100644
--- a/content/browser/web_contents/web_contents_impl.cc
+++ b/content/browser/web_contents/web_contents_impl.cc
@@ -132,6 +132,7 @@
 #if defined(OS_ANDROID)
 #include "content/browser/android/content_video_view.h"
 #include "content/browser/android/date_time_chooser_android.h"
+#include "content/browser/media/android/browser_media_session_manager.h"
 #include "content/browser/media/android/media_web_contents_observer_android.h"
 #include "content/browser/web_contents/web_contents_android.h"
 #endif  // OS_ANDROID
@@ -3814,10 +3815,19 @@ void WebContentsImpl::OnUpdateFaviconURL(
 
 void WebContentsImpl::OnMediaSessionStateChanged() {
   MediaSession* session = MediaSession::Get(this);
+  base::Optional<MediaMetadata> metadata;
+#if defined(OS_ANDROID)

[whywhat, 2016/09/13 16:23:26]

does it have to be android only? I thought we have MediaSession on desktop
behind the flag.

[Zhiqiang Zhang (Slow), 2016/09/13 17:15:56]

Yes, BrowserMediaSessionManager is in content/browser/media/android/

+  BrowserMediaSessionManager* session_manager =
+      static_cast<MediaWebContentsObserverAndroid*>(
+          media_web_contents_observer())
+          ->GetMediaSessionManager(GetMainFrame());
+  if (session_manager->media_metadata()) {
+    metadata = *session_manager->media_metadata();
+  }
+#endif  // defined(OS_ANDROID)
   FOR_EACH_OBSERVER(WebContentsObserver, observers_,
                     MediaSessionStateChanged(session->IsControllable(),
-                                             session->IsSuspended(),
-                                             session->metadata()));
+                                             session->IsSuspended(), metadata));
 }
 
 void WebContentsImpl::ResumeMediaSession() {