DevTools: make toolbar button click targets square

Source/devtools/front_end/ui/splitWidget.css

 /*
  * 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
  * notice, this list of conditions and the following disclaimer.
  *
@@ skipping 90 matching lines @@
     position: absolute;
     -webkit-mask-image: url(Images/toolbarButtonGlyphs.png);
     -webkit-mask-size: 352px 144px;
     height: 16px;
     width: 16px;
     border: none;
     z-index: 20;
     background-color: rgba(0, 0, 0, 0.6);
 }
 
+.shadow-split-widget button.sidebar-show-hide-button:hover {
+    background-color: black;
+}
+
 .shadow-split-widget button.sidebar-show-hide-button:disabled {
     background-color: rgba(0, 0, 0, 0.35);
 }
 
 @media (-webkit-min-device-pixel-ratio: 1.5) {
 .shadow-split-widget button.sidebar-show-hide-button {
     -webkit-mask-image: url(Images/toolbarButtonGlyphs_2x.png);
 }
 } /* media */
 
 .shadow-split-widget button.left-sidebar-show-hide-button,
 .shadow-split-widget button.top-sidebar-show-hide-button {
-    top: 3px;
-    left: 4px;
+    top: 5px;
+    left: 5px;
 }
 
 :host-context(.material) .shadow-split-widget button.left-sidebar-show-hide-button,
 :host-context(.material) .shadow-split-widget button.top-sidebar-show-hide-button {
     top: 5px;
 }
 
 .shadow-split-widget button.left-sidebar-show-hide-button:active,
 .shadow-split-widget button.top-sidebar-show-hide-button:active {
     top: 4px;
     left: 3px;
 }
 
 .shadow-split-widget button.right-sidebar-show-hide-button {
-    top: 3px;
-    right:2px;
+    top: 5px;
+    right:4px;
 }
 
 :host-context(.material) .shadow-split-widget button.right-sidebar-show-hide-button {
     top: 5px;
     right: 5px;
 }
 
 .shadow-split-widget button.right-sidebar-show-hide-button:active {
     top: 4px;
     right: 1px;
@@ skipping 42 matching lines @@
 
 .shadow-split-widget button.bottom-sidebar-show-hide-button.toggled-show {
     -webkit-mask-position: -296px -76px; /* <| */
     transform: rotate(90deg);
 }
 
 .shadow-split-widget button.bottom-sidebar-show-hide-button.toggled-hide {
     -webkit-mask-position: -264px -76px; /* >| */
     transform: rotate(90deg);
 }