Adding UMA to record whether Pepper players have ever played sound

content/browser/media/session/pepper_playback_observer.h

Index: content/browser/media/session/pepper_playback_observer.h
diff --git a/content/browser/media/session/pepper_playback_observer.h b/content/browser/media/session/pepper_playback_observer.h
index 11c85fea0048ee67fd3a499e6dce8545d6707bfe..3b43e19726194f8a0bbbfccec1a98e283672d1ee 100644
--- a/content/browser/media/session/pepper_playback_observer.h
+++ b/content/browser/media/session/pepper_playback_observer.h
@@ -35,6 +35,12 @@ class PepperPlaybackObserver {
       std::map<int32_t, std::unique_ptr<PepperPlayerDelegate>>;
   PlayersMap players_map_;
 
+  // Map for whether Pepper players have ever played sound.
+  // Used for recording UMA.
+  using PlayersPlayedSoundMap =
+      std::map<int32_t, bool>;
+  PlayersPlayedSoundMap players_played_sound_map_;
+
   // Weak reference to WebContents.
   WebContentsImpl* contents_;