[DevTools] Expose left and right toolbar in TabbedPane.

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

 /*
  * Copyright (C) 2006, 2007, 2008 Apple Inc.  All rights reserved.
  * Copyright (C) 2009 Anthony Ricaud <rik@webkit.org>
  * Copyright (C) 2011 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:
  *
  * 1. Redistributions of source code must retain the above copyright
@@ skipping 250 matching lines @@
 }
 
 .tabbed-pane-header-tab.disabled {
     opacity: 0.5;
     pointer-events: none;
 }
 
 .tabbed-pane-header.tabbed-pane-no-header-background {
     background-color: transparent;
 }
+
+.tabbed-pane-left-toolbar {
+    margin-right: -4px;
+    flex: none;
+}
+
+.tabbed-pane-right-toolbar {
+    margin-left: -4px;
+    flex: none;
+}