Add an explicit full-screen button.

remoting/webapp/window_frame.css

 /* 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.
  */
 
 html.apps-v2,
 html.apps-v2 body {
   height: 100%;
   width: 100%;
 }
@@ skipping 97 matching lines @@
 /* Remove dark borders for elements that are adjacent an existing border. */
 .window-close::after {
   border-right: none;
 }
 
 .window-controls-stub::after {
   border-bottom: none;
   border-right: none;
 }
 
-/* The Disconnect and Options buttons are only displayed when connected. */
+/* The Disconnect, full-screen and options buttons are only displayed when
+   connected. */
 body:not(.connected) .window-disconnect,
+body:not(.connected) .window-fullscreen,
 body:not(.connected) .window-options {
   display: none;
 }
 
 
 /*
  * When in full-screen mode, significant changes are made:
  * - The scroll-bars are removed.
  * - The window controls have a border (so the left-border of the first button
  *   is not needed).
  * - The window title is not displayed.
  * - The stub is visible.
  * - The window controls gain transition effects for position and opacity and
  *   auto-hide behind the top edge of the screen.
  * - A border is added to the window controls to ensure they stand out against
  *   any desktop.
  * - The window border is removed.
+ * - The full-screen button is removed.
  */
 
 html.apps-v2 body.fullscreen #scroller {
   height: 100%;
   overflow: hidden;
 }
 
 body.fullscreen .title-bar {
   border: 1px solid #a6a6a6;
 }
@@ skipping 28 matching lines @@
 body.fullscreen .title-bar.opened,
 body.fullscreen .title-bar.preview {
   top: -4px;
   opacity: 1.0;
   box-shadow: 1px 1px 10px rgba(0, 0, 0, 0.5);
 }
 
 .fullscreen .title-bar.opened .window-controls-stub {
   background-color: #a6a6a6;
 }
+
+body.fullscreen .window-fullscreen {
+  display: none;
+}