DevTools: add a navigator menu with grouping options.

third_party/WebKit/Source/devtools/front_end/ui/softContextMenu.css

 /*
  * Copyright (c) 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.
  */
 
 :host {
     position: absolute;
     border: 1px solid rgba(196, 196, 196, 0.9);
     border-top: 1px solid rgba(196, 196, 196, 0.5);
@@ skipping 11 matching lines @@
     width: 100%;
     line-height: 14px;
     font-size: 12px;
     border-top: 1px solid transparent;
     border-bottom: 1px solid transparent;
     padding: 2px 7px 2px 8px;
     margin: 0 13px 0 0;
     white-space: nowrap;
 }
 
+.soft-context-menu-disabled {
+    color: #999;
+    pointer-events: none;
+}
+
 .soft-context-menu-separator {
     height: 10px;
     margin: 0 1px;
 }
 
 .soft-context-menu-separator > .separator-line {
     margin: 0;
     height: 5px;
     border-bottom: 1px solid rgb(222, 222, 222);
     pointer-events: none;
@@ skipping 59 matching lines @@
     display: inline-block;
     pointer-events: none;
     margin: auto 5px auto 0px;
 }
 
 @media (-webkit-min-device-pixel-ratio: 1.5) {
 .checkmark {
     background-image: url(Images/toolbarButtonGlyphs_2x.png);
 }
 }