DevTools: do not respect Chrome theme in DevTools, align toolbar items.

Source/devtools/front_end/sidebarPane.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 80 matching lines @@
 
 .sidebar-pane-title::before {
     background-position: -4px -96px;
 }
 
 .sidebar-pane-title.expanded::before {
     background-position: -20px -96px;
 }
 
 .sidebar-pane > .toolbar {
-    border-bottom: 1px solid #ddd;
+    border-bottom: 1px solid #f1f1f1;
 }
 
 .sidebar-pane > .toolbar > * {
     pointer-events: auto;
 }
 
 .sidebar-pane-title > .toolbar {
     position: absolute;
     right: 0;
     top: -3px;
@@ skipping 27 matching lines @@
     visibility: hidden;
 }
 
 .styles-section.matched-styles:not(.read-only):hover .sidebar-pane-button-new-rule {
     visibility: visible;
 }
 
 .sidebar-pane-button-new-rule:hover {
     background-position: -23px 0;
 }