Add unit-tests for MenuButton and simplify implementation.

remoting/webapp/menu_button.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.
  */
 
 .menu-button {
   position: relative;
 }
 
 .menu-button-activator + ul {
-  visibility: hidden;

[Jamie, 2014/07/18 01:37:18]

visibility: hidden doesn't allow for verification using offsetWidth/Height. I
could use getComputedStyle instead; any preference?

[kelvinp, 2014/07/18 18:47:39]

I think either way is fine.  Personally, I prefer getComputedStyle and check for
the visibility or display or the element instead of checking the width and
height.

[Jamie, 2014/07/18 19:46:12]

As discussed in person, since showing or hiding the element requires a
re-layout, it would need an asynchronous browser test to do it that way, and
might be more flaky. I'm going to stick with this approach.

+  display: none;
   position: absolute;
 }
 
 .menu-button-activator + ul:not(.right-align) {
   left: 1px;
 }
 
 .menu-button-activator + ul.right-align {
   right: 1px;
 }
 
 .menu-button-activator.active + ul {
-  visibility: visible;
+  display: block;
 }
 
 .menu-button-activator.active {
   background-color: #EEE;
   background-image: -webkit-gradient(linear, left top, left bottom,
                                      from(#EEE), to(#E0E0E0));
   box-shadow: inset 0px 1px 2px rgba(0, 0, 0, 0.1);
   border: 1px solid #CCC;
   color: #333;
 }
@@ skipping 45 matching lines @@
 }
 
 .help-icon:hover, .help-icon.active {
   opacity: 0.5;
 }
 
 #help-feedback-toolbar {
   margin-left: 8px;
   margin-top: 4px;
 }