Plumb audio focus support for spitzer clients.

content/browser/media/media_web_contents_observer.h

Index: content/browser/media/media_web_contents_observer.h
diff --git a/content/browser/media/media_web_contents_observer.h b/content/browser/media/media_web_contents_observer.h
index d902dc9608d40b80ac856590de24396884c16d09..6dcbfc186909c8f8ada54279e2d209d0792a9d14 100644
--- a/content/browser/media/media_web_contents_observer.h
+++ b/content/browser/media/media_web_contents_observer.h
@@ -11,6 +11,7 @@
 #include <set>
 #include <vector>
 
+#include "base/callback_forward.h"
 #include "base/macros.h"
 #include "base/memory/scoped_ptr.h"
 #include "content/common/content_export.h"
@@ -47,6 +48,26 @@ class CONTENT_EXPORT MediaWebContentsObserver : public WebContentsObserver {
     return !!video_power_save_blocker_;
   }
 
+  // Executes |focus_cb| on the calling thread once the given render frame has
+  // audio focus.  Clients are responsible for invalidating |focus_cb| if their
+  // lifetime changes or the callback is unnecessary.
+  //
+  // This call does not request focus, it only waits for a focus request for the
+  // given render frame to be approved.  The focus request must be initiated via
+  // the WebMediaPlayerDelegate interface in the renderer.
+  //
+  // Focus is never denied, only delayed until the underlying platform approves
+  // the request.  |focus_cb| may never be called if the given render frame goes
+  // away.  Callers are expected to have their own monitoring for such events in
+  // order to properly handle the lack of a callback.
+  static void WaitForAudioFocusAsync(int render_process_id,
+                                     int render_frame_id,
+                                     const base::Closure& focus_cb);
+
+ protected:
+  virtual void WaitForAudioFocusAsyncInternal(int render_frame_id,
+                                              const base::Closure& focus_cb);
+
  private:
   void OnMediaDestroyed(RenderFrameHost* render_frame_host, int delegate_id);
   void OnMediaPaused(RenderFrameHost* render_frame_host,