[Android] A prototype of the interactive media notification.

content/public/browser/web_contents_delegate.h

Index: content/public/browser/web_contents_delegate.h
diff --git a/content/public/browser/web_contents_delegate.h b/content/public/browser/web_contents_delegate.h
index 34d39f779cd801cc983f6d449a9075a16d5746aa..be239bab6a5c912b27dd394045a0ea18c2c7b58d 100644
--- a/content/public/browser/web_contents_delegate.h
+++ b/content/public/browser/web_contents_delegate.h
@@ -405,6 +405,9 @@ class CONTENT_EXPORT WebContentsDelegate {
                                    int version,
                                    const std::vector<gfx::RectF>& rects,
                                    const gfx::RectF& active_rect) {}
+
+  // Notifies the tab that the state relevant to the media controls has changed.
+  virtual void UpdateMediaControls(WebContents* web_contents) {}

[Ted C, 2015/06/26 00:43:55]

Why does this exist here?

WebContentsObserver already has methods MediaStartedPlaying & MediaPaused.  I'm
not a big fan of having this exist in the delegate and the observer for very
similar functionality.

I would rather us make the observer more robust to ensure it covers the cases
you are trying to accomplish (or just ensuring the two above methods are called
when appropriate).

[whywhat, 2015/06/26 19:29:32]

So these methods are only used for Chromecast as far as I can see and we don't
really bind the media controls notification to a single player playing/paused.
So MediaSession from media_session.cc would call something like
WebContents::MediaSessionChanged() and that would notify the
WebContentsObservers that would use the MediaControlsDelegate to get what they
need and update the controls.

WDYT?
Where would I initialize such an observer in Chrome for Android?

[Ted C, 2015/06/30 04:56:13]

The problem I have with it being in both WebContentsDelegate and
WebContentsObserver is that embedders of the content layer have no real idea of
when to use one or the other.

If the existing ones are in WebContentsObserver, I would rather be consistent
and add further clarification of when to use one over the other.
You would initialize it in Tab/ChromeTab.  There are already a few examples of
an self contained observer that is a good example of what I'm referring to.

https://code.google.com/p/chromium/codesearch#chromium/src/chrome/android/jav...
https://code.google.com/p/chromium/codesearch#chromium/src/chrome/android/jav...

That is really the example of how I would like to see the chrome side
implemented.

Even if the WebContentsDelegate approach is what needs to be done, you could add
a TabObserver method to still keep the bulk of the code out of the tab logic
itself.

 #endif
 
   // Invoked when the preferred size of the contents has been changed.