DevTools: hide emulation bits that are available in responsive design toolbar from the drawer.

Source/devtools/front_end/overrides.css

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 48 matching lines @@
 
 .overrides-view .tabbed-pane-header-tab {
     background-color: transparent;
     border: none transparent;
     font-weight: normal;
     text-shadow: none;
     color: #777;
     height: 22px;
     padding-left: 0;
     padding-left: 10px;
-    border-left: 4px solid transparent;
+    border-left: 6px solid transparent;
 }
 
 .overrides-view .tabbed-pane-header-tab:not(.selected) {
     cursor: pointer !important;
 }
 
 .overrides-view .tabbed-pane-header-tab.selected {
     color: inherit;
     border: none transparent;
-    border-left: 4px solid #666;
+    border-left: 6px solid #666;
 }
 
 .overrides-view fieldset {
     border: none;
     padding: 0 0 5px 15px;
 }
 
 .overrides-view fieldset p {
     display: inline-block;
     padding: 0;
@@ skipping 161 matching lines @@
 
 @media (-webkit-min-device-pixel-ratio: 1.5) {
 .overrides-view .overrides-footer::before {
     background-image: url(Images/statusbarButtonGlyphs_2x.png);
 }
 } /* media */
 
 .overrides-view .overrides-footer .warning-icon-small {
     margin-right: 3px;
 }