DevTools: move emulation button into the base App.js.

Source/devtools/front_end/inspector.css

 /*
  * Copyright (C) 2006, 2007, 2008 Apple Inc.  All rights reserved.
  * Copyright (C) 2009 Anthony Ricaud <rik@webkit.org>
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
@@ skipping 2276 matching lines @@
     left: 0;
     overflow: hidden;
     border-left: 1px solid rgb(184, 184, 184);
     margin-left: -1px;
 }
 
 .node-search-status-bar-item .glyph {
     -webkit-mask-position: -224px -24px;
 }
 
-.responsive-design-status-bar-item .glyph {
+.emulation-status-bar-item .glyph {
     -webkit-mask-position: -164px 0px;
 }
 
 .delete-storage-status-bar-item .glyph {
     -webkit-mask-position: -128px 0;
 }
 
 .clear-storage-status-bar-item .glyph {
     -webkit-mask-position: -64px 0;
 }
@@ skipping 588 matching lines @@
 }
 
 select.drop-down-menu {
     border: none;
     -webkit-appearance: none;
 }
 
 .viewport-control-gap-element {
     color: transparent;
 }