Link MediaSessionTabHelper with native MediaSession [CL is going to be split]

content/public/android/java/src/org/chromium/content_public/browser/WebContents.java

Index: content/public/android/java/src/org/chromium/content_public/browser/WebContents.java
diff --git a/content/public/android/java/src/org/chromium/content_public/browser/WebContents.java b/content/public/android/java/src/org/chromium/content_public/browser/WebContents.java
index fce0c95cb94d940e84e1b6b57e67e9306d1de840..9cd74b41cad0c9b3003a6d915d59f24b511210f6 100644
--- a/content/public/android/java/src/org/chromium/content_public/browser/WebContents.java
+++ b/content/public/android/java/src/org/chromium/content_public/browser/WebContents.java
@@ -306,20 +306,7 @@ public interface WebContents extends Parcelable {
      */
     void requestAccessibilitySnapshot(AccessibilitySnapshotCallback callback);
 
-    /**
-     * Resumes the current media session.
-     */
-    void resumeMediaSession();
-
-    /**
-     * Suspends the current media session.
-     */
-    void suspendMediaSession();
-
-    /**
-     * Stops the current media session.
-     */
-    void stopMediaSession();
+    void addMediaSessionDelegate(MediaSessionDelegate delegate);

[boliu, 2016/10/19 20:39:40]

nit: s/add/set/ ?

[Zhiqiang Zhang (Slow), 2016/10/20 16:22:32]

Not really, we allow adding multiple MediaSessionDelegates.

[boliu, 2016/10/20 16:28:33]

Usually you can have only one "delegate", but multiple "observers". Are these
supposed to be observers?

[Zhiqiang Zhang (Slow), 2016/10/20 17:07:03]

Actually "delegate" inherits from "observer", a delegate can both observe
MediaSession changes and perform actions on MediaSession. Ideally this could be
solved by adding a Java counterpart of MediaSession, but we don't have plans.

We haven't come up with a better name yet. Do you have any suggestion? Or Anton
has some ideas?

[boliu, 2016/10/20 17:10:19]

Feels like that fact should live in the embedder not content.

Like WebContents has a Delegate and a bunch of Observers. It doesn't care if the
embedder's Delegate also implements the Observer. (Although embedder have to be
careful of ownership.(

On the other hand, does this really need to be that complicated? I'd suggest
trying to simplify if possible, without actually knowing any of this code

 
     /**
      * Add an observer to the WebContents