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 0e3c980a42b1eaae62d17132aaca3a905fc10692..57543bcebbbd823e3c0eb22dcac11fdd67e4645f 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 +48,17 @@ class CONTENT_EXPORT MediaWebContentsObserver : public WebContentsObserver {
     return video_power_save_blocker_;
   }
 
+  // Executes |on_focus_cb| once the given render frame has audio focus.  Will
+  // be run on the calling thread.  Clients are responsible for invalidating
+  // |on_focus_cb| if their lifetime changes or the callback is unnecessary.
+  static void HasAudioFocus(int render_process_id,
+                            int render_frame_id,
+                            const base::Closure& on_focus_cb);
+
+ protected:
+  virtual void CheckFocus(int render_frame_id,
+                          const base::Closure& on_focus_cb);
+
  private:
   void OnMediaDestroyedNotification(RenderFrameHost* render_frame_host,
                                     int64_t player_cookie);