Adds histograms for casting feature of Video Player

ui/file_manager/video_player/js/cast/cast_video_element.js

 // Copyright 2014 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.
 
 /**
  * Interval for updating media info (in ms).
  * @type {number}
  * @const
  */
 var MEDIA_UPDATE_INTERVAL = 250;
@@ skipping 468 matching lines @@
         this.dispatchEvent(new Event('pause'));
 
       this.currentMediaPlayerState_ = newState;
     }
     if (this.currentMediaCurrentTime_ !== media.getEstimatedTime()) {
       this.currentMediaCurrentTime_ = media.getEstimatedTime();
       this.dispatchEvent(new Event('timeupdate'));
     }
 
     if (this.currentMediaDuration_ !== media.media.duration) {
+      metrics.recordCastedVideoLength(this.currentMediaDuration_);
+
       this.currentMediaDuration_ = media.media.duration;
       this.dispatchEvent(new Event('durationchange'));
     }
 
     // Media is being unloaded.
     if (!alive) {
       this.unloadMedia_();
       return;
     }
   },
 };