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 d902dc9608d40b80ac856590de24396884c16d09..9e2044e72e968b930adcb5e544a23425b1dead5a 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"
@@ -72,8 +71,8 @@ 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.