Moving this nonessential bug to the next milestone.

For more details visit https://www.chromium.org/issue-tracking/autotriage - Your friendly Sheriffbot

Maybe I need to start working on this one to prepare for the upcoming MediaMetadata changes on the Chrome side, since I don't want the metadata be passed too frequently, especially for MediaImage.

What I now have in mind is to have MediaSessionStateChanged() only for activate/deactivate signals, and MediaMetadataChanged() for metadata update. WebContentsImpl.java will have to store a copy of java MediaMetadata since MediaSessionTabHelper will ignore the metadata if the tab doesn't have audio focus. The copy of MediaMetadata should be light enough.

WDYT guys?

Sounds good! I think we can call the method MediaSessionMetadataChanged() but that's just naming :)

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/dea696202a6c6abfbb156706a722c74b6e4fc89c

commit dea696202a6c6abfbb156706a722c74b6e4fc89c
Author: zqzhang <zqzhang@chromium.org>
Date: Thu Oct 13 10:26:51 2016

Split MediaSessionStateChanged() and MediaSessionMetadataChanged()

This CL splits the metadata out from MediaSessionStateChanged() into
another observer function, in order to avoid sending MediaMetadata
through Java every time, which is very expensive and makes the
MediaSessionTabHelper logic complex.

BUG= 621855 

Review-Url: https://codereview.chromium.org/2411723002
Cr-Commit-Position: refs/heads/master@{#424997}

[modify] https://crrev.com/dea696202a6c6abfbb156706a722c74b6e4fc89c/chrome/android/java/src/org/chromium/chrome/browser/media/ui/MediaSessionTabHelper.java
[modify] https://crrev.com/dea696202a6c6abfbb156706a722c74b6e4fc89c/chrome/android/javatests/src/org/chromium/chrome/browser/media/ui/NotificationTitleUpdatedTest.java
[modify] https://crrev.com/dea696202a6c6abfbb156706a722c74b6e4fc89c/chromecast/browser/cast_media_blocker.cc
[modify] https://crrev.com/dea696202a6c6abfbb156706a722c74b6e4fc89c/chromecast/browser/cast_media_blocker.h
[modify] https://crrev.com/dea696202a6c6abfbb156706a722c74b6e4fc89c/content/browser/android/web_contents_observer_proxy.cc
[modify] https://crrev.com/dea696202a6c6abfbb156706a722c74b6e4fc89c/content/browser/android/web_contents_observer_proxy.h
[modify] https://crrev.com/dea696202a6c6abfbb156706a722c74b6e4fc89c/content/browser/media/session/media_session.cc
[modify] https://crrev.com/dea696202a6c6abfbb156706a722c74b6e4fc89c/content/browser/media/session/media_session_browsertest.cc
[modify] https://crrev.com/dea696202a6c6abfbb156706a722c74b6e4fc89c/content/browser/web_contents/web_contents_impl.cc
[modify] https://crrev.com/dea696202a6c6abfbb156706a722c74b6e4fc89c/content/browser/web_contents/web_contents_impl.h
[modify] https://crrev.com/dea696202a6c6abfbb156706a722c74b6e4fc89c/content/public/android/java/src/org/chromium/content/browser/webcontents/WebContentsObserverProxy.java
[modify] https://crrev.com/dea696202a6c6abfbb156706a722c74b6e4fc89c/content/public/android/java/src/org/chromium/content_public/browser/WebContentsObserver.java
[modify] https://crrev.com/dea696202a6c6abfbb156706a722c74b6e4fc89c/content/public/browser/web_contents_observer.h