Show the window controls for 3s on entering full-screen mode.

remoting/webapp/window_frame.js

 // 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.
 
 /**
  * @fileoverview
  * Apps v2 custom title bar implementation
  */
 
 'use strict';
@@ skipping 79 matching lines @@
   }
 
   // Ensure that tool-tips are always correct.
   this.updateMaximizeOrRestoreIconTitle_();
   chrome.app.window.current().onMaximized.addListener(
       this.updateMaximizeOrRestoreIconTitle_.bind(this));
   chrome.app.window.current().onRestored.addListener(
       this.updateMaximizeOrRestoreIconTitle_.bind(this));
   chrome.app.window.current().onFullscreened.addListener(
       this.updateMaximizeOrRestoreIconTitle_.bind(this));
+  chrome.app.window.current().onFullscreened.addListener(
+      this.showWindowControlsPreview_.bind(this));
 };
 
 /**
  * @param {remoting.ClientSession} clientSession The client session, or null if
  *     there is no connection.
  */
 remoting.WindowFrame.prototype.setClientSession = function(clientSession) {
   this.optionsMenu_.setClientSession(clientSession);
   this.clientSession_ = clientSession;
   var windowTitle = document.head.querySelector('title');
@@ skipping 108 matching lines @@
 };
 
 /**
  * Callback invoked when the options menu is shown.
  * @private
  */
 remoting.WindowFrame.prototype.onHideOptionsMenu_ = function() {
   this.hoverTarget_.classList.remove('menu-opened');
 };
 
+/**
+ * Show the window controls for a few seconds
+ *
+ * @private
+ */
+remoting.WindowFrame.prototype.showWindowControlsPreview_ = function() {
+  /**
+   * @type {HTMLElement}
+   */
+  var target =  this.hoverTarget_;
+  var kPreviewTimeoutMs = 3000;
+  var hidePreview = function() {
+    target.classList.remove('preview');
+  };
+  target.classList.add('preview');
+  window.setTimeout(hidePreview, kPreviewTimeoutMs);
+};
+
 
 /** @type {remoting.WindowFrame} */
-remoting.windowFrame = null;
+remoting.windowFrame = null;