Refactor media out of WebContentsImpl to MediaWebContentsObserver.

chrome/browser/engagement/site_engagement_helper.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CHROME_BROWSER_ENGAGEMENT_SITE_ENGAGEMENT_HELPER_H_
 #define CHROME_BROWSER_ENGAGEMENT_SITE_ENGAGEMENT_HELPER_H_
 
 #include "base/macros.h"
 #include "base/timer/timer.h"
 #include "chrome/browser/engagement/site_engagement_metrics.h"
@@ skipping 112 matching lines @@
   //
   // When media begins playing in the main frame of a tab, the tracker is
   // triggered with an initial delay. It then wakes up every
   // |g_seconds_to_pause_engagement_detection| and notes the visible/hidden
   // state of the tab, as well as whether media is still playing.
   class MediaTracker : public PeriodicTracker,
                        public content::WebContentsObserver {
    public:
     MediaTracker(SiteEngagementHelper* helper,
                  content::WebContents* web_contents);
+    ~MediaTracker() override;
 
    private:
     friend class SiteEngagementHelperTest;
 
     void TrackingStarted() override;
 
     // content::WebContentsObserver overrides.
-    void MediaStartedPlaying() override;
-    void MediaPaused() override;
+    void MediaStartedPlaying(const MediaPlayerId& id) override;
+    void MediaStoppedPlaying(const MediaPlayerId& id) override;
     void WasShown() override;
     void WasHidden() override;
 
     bool is_hidden_;
-    bool is_playing_;
+    std::vector<MediaPlayerId> active_media_players_;
   };
 
   explicit SiteEngagementHelper(content::WebContents* web_contents);
   friend class content::WebContentsUserData<SiteEngagementHelper>;
   friend class SiteEngagementHelperTest;
 
   // Ask the SiteEngagementService to record engagement via user input at the
   // current WebContents URL.
   void RecordUserInput(SiteEngagementMetrics::EngagementType type);
 
   // Ask the SiteEngagementService to record engagement via media playing at the
   // current WebContents URL.
   void RecordMediaPlaying(bool is_hidden);
 
   InputTracker input_tracker_;
   MediaTracker media_tracker_;
   bool record_engagement_;
 
   DISALLOW_COPY_AND_ASSIGN(SiteEngagementHelper);
 };
 
 #endif  // CHROME_BROWSER_ENGAGEMENT_SITE_ENGAGEMENT_HELPER_H_