Video Player: Support Media Router to cast Drive videos.

ui/file_manager/video_player/css/media_controls.css

 /* Copyright (c) 2012 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. */
 
 /* Common styles for media buttons. */
 
 .media-button {
   background-position: center;
   background-repeat: no-repeat;
   flex: none;
@@ skipping 113 matching lines @@
   background: rgb(250, 250, 250);
   display: flex;
   font-size: 13px;
   height: 32px;
   padding: 8px;
   pointer-events: auto;
 }
 
 /* Cast button. */
 
-.media-button.cast {
+.media-button.cast,
+.media-button.cast-button {
   background-image: -webkit-image-set(
     url(../images/media/media_chromecast.png) 1x,
     url(../images/media/2x/media_chromecast.png) 2x);
   display: none;
   border-radius: 2px;
 }
 
 /* Reset browser's button style. */
 .media-button.cast {
   background-color: transparent;
   border: none;
   cursor: pointer;
   outline: none;
 }
 
-#video-player[cast-available][castable] .media-button.cast {
+#video-player[cast-available][castable] .media-button.cast,
+#video-player[mr-cast-available][castable] .media-button.cast-button {
   display: block;
 }
 
-#video-player[casting] .media-button.cast {
+#video-player[casting] .media-button.cast,
+#video-player[casting] .media-button.cast-button {
   background-image: -webkit-image-set(
     url(../images/media/media_chromecast_casting.png) 1x,
     url(../images/media/2x/media_chromecast_casting.png) 2x);
 }
 
 .media-button.cast:focus:not(.using-mouse) {
   box-shadow: 0 0 0 1px rgba(66, 133, 244, 0.5);
 }
 
 /* Fullscreen button. */
@@ skipping 105 matching lines @@
     url(../images/media/media_play_onscreen.png) 1x,
     url(../images/media/2x/media_play_onscreen.png) 2x);
 }
 
 .playback-state-icon[state='pause'] {
   -webkit-animation: blowup 500ms;
   background-image: -webkit-image-set(
     url(../images/media/media_pause_onscreen.png) 1x,
     url(../images/media/2x/media_pause_onscreen.png) 2x);
 }