[Media Router] Add UMA metrics to record the load time for route controls

chrome/browser/resources/media_router/media_router_browser_api.js

 // Copyright 2017 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.
 
 // API invoked by this UI to communicate with the browser WebUI message handler.
 cr.define('media_router.browserApi', function() {
   'use strict';
 
   /**
    * Indicates that the user has acknowledged the first run flow.
@@ skipping 197 matching lines @@
    * Reports the time, in ms, it took for the user to close the dialog without
    * taking any other action.
    *
    * @param {number} timeMs
    */
   function reportTimeToInitialActionClose(timeMs) {
     chrome.send('reportTimeToInitialActionClose', [timeMs]);
   }
 
   /**
+   * Reports the time, in ms, it took the WebUI route controller to load media
+   * status info.
+   *
+   * @param {number} timeMs
+   */
+  function reportWebUIRouteControllerLoaded(timeMs) {
+    chrome.send('reportWebUIRouteControllerLoaded', [timeMs]);
+  }
+
+  /**
    * Requests data to initialize the WebUI with.
    * The data will be returned via media_router.ui.setInitialData.
    */
   function requestInitialData() {
     chrome.send('requestInitialData');
   }
 
   /**
    * Requests that a media route be started with the given sink.
    *
@@ skipping 74 matching lines @@
     reportFilter: reportFilter,
     reportInitialAction: reportInitialAction,
     reportInitialState: reportInitialState,
     reportNavigateToView: reportNavigateToView,
     reportRouteCreation: reportRouteCreation,
     reportRouteCreationOutcome: reportRouteCreationOutcome,
     reportSelectedCastMode: reportSelectedCastMode,
     reportSinkCount: reportSinkCount,
     reportTimeToClickSink: reportTimeToClickSink,
     reportTimeToInitialActionClose: reportTimeToInitialActionClose,
+    reportWebUIRouteControllerLoaded: reportWebUIRouteControllerLoaded,
     requestInitialData: requestInitialData,
     requestRoute: requestRoute,
     searchSinksAndCreateRoute: searchSinksAndCreateRoute,
     seekCurrentMedia: seekCurrentMedia,
     setCurrentMediaMute: setCurrentMediaMute,
     setCurrentMediaVolume: setCurrentMediaVolume,
   };
 });