Adds histograms for casting feature of Video Player

ui/file_manager/video_player/js/video_player.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.
 
 /**
  * @param {Element} playerContainer Main container.
  * @param {Element} videoContainer Container for the video element.
  * @param {Element} controlsContainer Container for video controls.
  * @constructor
  */
@@ skipping 300 matching lines @@
             document.querySelector('#thumbnail').style.backgroundImage = '';
           }
         })
         .catch(function() {
           // Shows no image on error.
           document.querySelector('#thumbnail').style.backgroundImage = '';
         });
 
     var videoElementInitializePromise;
     if (this.currentCast_) {
+      metrics.recordUserAction('CastVideo');

[Ilya Sherman, 2014/12/02 23:45:10]

This looks like you're recording a user action rather than a histogram.  I'd
recommend recording your set of user actions within one or more enumerated
histograms; but if you prefer user actions, then you'll need to add these to the
actions.xml file rather than the histograms.xml one.

[yoshiki, 2014/12/08 02:52:29]

Thanks for guidance. I've changed it to recording the type of play (local play
or cast). I think it is metrics rather than user action.

+
       videoPlayerElement.setAttribute('casting', true);
 
       document.querySelector('#cast-name').textContent =
           this.currentCast_.friendlyName;
 
       videoPlayerElement.setAttribute('castable', true);
 
       videoElementInitializePromise = media.isAvailableForCast()
           .then(function(result) {
             if (!result)
@@ skipping 52 matching lines @@
           }.wrap());
           this.videoElement_.addEventListener('pause', function() {
             chrome.power.releaseKeepAwake();
           }.wrap());
 
           this.videoElement_.load();
           callback();
         }.bind(this))
         // In case of error.
         .catch(function(error) {
+          if (this.currentCast_)
+            metrics.recordUserAction('CastVideoError');
+
           videoPlayerElement.removeAttribute('loading');
           console.error('Failed to initialize the video element.',
                         error.stack || error);
           this.controls_.showErrorMessage(
               'VIDEO_PLAYER_VIDEO_FILE_UNSUPPORTED');
           callback();
         }.bind(this));
   }.wrap(this));
 };
 
@@ skipping 258 matching lines @@
   }.wrap(null));
 }
 
 var initPromise = Promise.all(
     [new Promise(initVideos.wrap(null)),
      new Promise(initStrings.wrap(null)),
      new Promise(util.addPageLoadHandler.wrap(null))]);
 
 initPromise.then(function(results) {
   var videos = results[0];
+
+  metrics.recordUserAction('OpenVideoPlayer');
+  metrics.recordSmallCount('NumberOfOpenedFiles', videos.length);
+
   player.prepare(videos);
   return new Promise(player.playFirstVideo.wrap(player));
 }.wrap(null));