Implement MediaMetadata artwork in content

content/browser/media/android/media_web_contents_observer_android.cc

Index: content/browser/media/android/media_web_contents_observer_android.cc
diff --git a/content/browser/media/android/media_web_contents_observer_android.cc b/content/browser/media/android/media_web_contents_observer_android.cc
index 5a6c451f13a4a9c0a14900372580293ec1b2c368..2f5a14f60122ad806d9c97b1ec0e6fa26c7ac6aa 100644
--- a/content/browser/media/android/media_web_contents_observer_android.cc
+++ b/content/browser/media/android/media_web_contents_observer_android.cc
@@ -80,6 +80,11 @@ MediaWebContentsObserverAndroid::GetSurfaceViewManager(
   return manager;
 }
 
+void MediaWebContentsObserverAndroid::SetMediaSessionManagerForTest(
+    RenderFrameHost* render_frame_host, BrowserMediaSessionManager* manager) {

[dcheng, 2016/07/05 02:36:55]

Nit: please pass |manager| through as a std::unique_ptr.

[Zhiqiang Zhang (Slow), 2016/07/05 15:30:30]

Done. Though I think we are putting too much magic code here for test. We need
base::WrapUnique on the call site, and need std::forward in this method since
media_session_managers_.set() uses copy ctor which is removed in
std::unique_ptr.

[dcheng, 2016/07/06 02:34:15]

If a pointer param is transferring ownership, it should be passed a unique_ptr,
regardless of whether or not it's in a test. The tradeoff is a bit more typing
to be explicit about ownership, but it turns out to be quite helpful in seeing
how ownership flows through a system.

+  media_session_managers_.set(render_frame_host, base::WrapUnique(manager));
+}
+
 void MediaWebContentsObserverAndroid::SuspendAllMediaPlayers() {
   web_contents()->ForEachFrame(
       base::Bind(&SuspendAllMediaPlayersInRenderFrame));