Video Player: Support Media Router to cast Drive videos.

ui/file_manager/video_player/js/media_controls.js

Index: ui/file_manager/video_player/js/media_controls.js
diff --git a/ui/file_manager/video_player/js/media_controls.js b/ui/file_manager/video_player/js/media_controls.js
index 3264fb5e2bbd91ad5c5dadd58b4f1afe55dac9cd..b8a244efca5d5d6b73067d2edcc41c89bc1e9912 100644
--- a/ui/file_manager/video_player/js/media_controls.js
+++ b/ui/file_manager/video_player/js/media_controls.js
@@ -861,7 +861,7 @@ function VideoControls(
   this.initVolumeControls();
   this.initSubtitlesButton();
 
-  // Create the cast button.
+  // Create the cast menu button.
   // We need to use <button> since cr.ui.MenuButton.decorate modifies prototype
   // chain, by which <files-icon-button> will not work correctly.
   // TODO(fukino): Find a way to use files-icon-button consistently.
@@ -873,6 +873,10 @@ function VideoControls(
   this.castButton_.appendChild(document.createElement('files-ripple'));
   cr.ui.decorate(this.castButton_, cr.ui.MenuButton);
 
+  // Create the cast button, which is a normal button and is used when we cast
+  // videos usign Media Router.
+  this.createButton('cast-button');
+
   if (opt_fullScreenToggle) {
     this.fullscreenButton_ =
         this.createButton('fullscreen', opt_fullScreenToggle);