Plumb audio focus support for spitzer clients.

content/browser/media/android/media_web_contents_observer_android.h

Index: content/browser/media/android/media_web_contents_observer_android.h
diff --git a/content/browser/media/android/media_web_contents_observer_android.h b/content/browser/media/android/media_web_contents_observer_android.h
index e60246817f7730774bf6bea536a45fbe406d2376..ba1db3c6bf6a119eb0fd1e4e479e38b5ad230896 100644
--- a/content/browser/media/android/media_web_contents_observer_android.h
+++ b/content/browser/media/android/media_web_contents_observer_android.h
@@ -7,6 +7,8 @@
 
 #include <stdint.h>
 
+#include <list>
+
 #include "base/containers/scoped_ptr_hash_map.h"
 #include "base/macros.h"
 #include "base/memory/scoped_ptr.h"
@@ -58,6 +60,10 @@ class CONTENT_EXPORT MediaWebContentsObserverAndroid
   bool OnMessageReceived(const IPC::Message& message,
                          RenderFrameHost* render_frame_host) override;
 
+ protected:
+  void WaitForAudioFocusAsyncInternal(int render_frame_id,

[mlamouri (slow - plz ping), 2016/02/03 15:20:52]

Add comment saying that `callback` may never be called if the frame associated
with `render_frame_id` is deleted.

+                                      const base::Closure& focus_cb) override;

[mlamouri (slow - plz ping), 2016/02/03 15:20:52]

nit: `callback`

+
  private:
   // Handles messages from the WebMediaPlayerDelegate; does not modify the
   // handled state since the superclass needs to handle these as well.
@@ -104,6 +110,11 @@ class CONTENT_EXPORT MediaWebContentsObserverAndroid
       std::map<MediaPlayerId, scoped_ptr<MediaSessionController>>;
   MediaSessionMap media_session_map_;

[mlamouri (slow - plz ping), 2016/02/03 15:20:52]

I was confused by your change because `media_session_map_` looks like a map of
all the media sessions but it's actually a map of all the controllers. Maybe
worth fixing in a follow-up?

 
+  // List of focus callbacks awaiting fulfillment; each entry is a render frame
+  // id and callback.  There may be multiple entries per render frame id.
+  using FocusWaiter = std::pair<int, base::Closure>;

[mlamouri (slow - plz ping), 2016/02/03 15:20:52]

nit: `using FocusCallback`? or `FocusCallbackWrapper`?

+  std::list<FocusWaiter> focus_waiters_;

[mlamouri (slow - plz ping), 2016/02/03 15:20:52]

nit: focus_callbacks_

+
   DISALLOW_COPY_AND_ASSIGN(MediaWebContentsObserverAndroid);
 };