DevTools: polish Mac UI (borders, alignment, line heights, images).

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 113 matching lines @@
     pointer-events: none;
 }
 
 .sidebar-pane-toolbar > * {
     pointer-events: auto;
 }
 
 .sidebar-pane-toolbar > .pane-title-button,
 .sidebar-pane-toolbar > label {
     float: right;
-    height: 17px;
+    height: 19px;
     background-color: transparent;
     border: none;
     background-repeat: no-repeat;
     margin: 1px 0 0 0;
     padding: 0;
     border-radius: 0;
     -webkit-appearance: none;
 }
 
 .sidebar-pane-toolbar > .pane-title-button {
@@ skipping 38 matching lines @@
 }
 
 .section > .header input[type=checkbox] {
     height: 1em;
     width: 1em;
     margin-left: 0;
     margin-top: 0;
     margin-bottom: 0.25em;
     vertical-align: bottom;
 }