media: Allow WMPI to send playing started notification while playing

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 93e21981fb79d756bd1c9eb6a3a7bbe002b8d08d..891d7c8be1fef3a3eb104457dea8d04abed1bb9e 100644
--- a/content/browser/media/media_web_contents_observer.h
+++ b/content/browser/media/media_web_contents_observer.h
@@ -9,7 +9,6 @@
 
 #include <map>
 #include <set>
-#include <vector>
 
 #include "base/macros.h"
 #include "base/memory/scoped_ptr.h"
@@ -79,8 +78,8 @@ class CONTENT_EXPORT MediaWebContentsObserver : public WebContentsObserver {
   void MaybeReleasePowerSaveBlockers();
 
   // Helper methods for adding or removing player entries in |player_map|.
-  using PlayerList = std::vector<int>;
-  using ActiveMediaPlayerMap = std::map<RenderFrameHost*, PlayerList>;
+  using PlayerSet = std::set<int>;
+  using ActiveMediaPlayerMap = std::map<RenderFrameHost*, PlayerSet>;
   void AddMediaPlayerEntry(const MediaPlayerId& id,
                            ActiveMediaPlayerMap* player_map);
   // Returns true if an entry is actually removed.