Video Player: Support Media Router to cast Drive videos.

ui/file_manager/video_player/css/media_controls.css

Index: ui/file_manager/video_player/css/media_controls.css
diff --git a/ui/file_manager/video_player/css/media_controls.css b/ui/file_manager/video_player/css/media_controls.css
index f2bd382f932f6c78b814b4f1e586799054063154..6c0ff616d022b822bc1e7f7ddbaf0a4234a2b794 100644
--- a/ui/file_manager/video_player/css/media_controls.css
+++ b/ui/file_manager/video_player/css/media_controls.css
@@ -131,7 +131,8 @@ paper-slider.volume {
 
 /* 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);
@@ -147,11 +148,13 @@ paper-slider.volume {
   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);