Switch from margin to padding for checkboxes and radio buttons.

chrome/browser/resources/shared/css/chrome_shared2_touch.css

 /* Copyright (c) 2012 The Chromium Authors. All rights reserved.
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file. */
 
 /* NB: do not include this file directly. Include chrome_shared2.css. If touch
  * optimization is enabled, these rules will be automatically loaded by the
  * SharedResourceDataSource. */
 
 <include src="chrome_shared2.css">
 
 /* TODO(kevers): Add [type='input'] and [type='password']. */
 input[type='search'] {
   padding-bottom: 6px;
   padding-top: 6px;
 }
 
-/* Additional padding to disambiguate controls on neighboring rows.
- * Ideally, the margin belongs on input[type=radio|checkbox] to be a more
- * general fix; however, this creates baseline problems as webkit is not
- * currently able to reconcile the baseline of a text-free inline box
- * containing a margin and fixed dimensions with neighboring content.
- * TODO(kevers): Reinvestigate once the baseline adjustment properties in
- * CSS3 are supported. */
+/* Margins are not touchable.  Use padding on the inner label instead to
+  increase the size of the touch target. */
 .checkbox,
 .radio {
-  margin: 12px 0;
+ margin: 0;
+}
+
+.checkbox label,
+.radio label {
+  padding-bottom: 7px;
+  padding-top: 7px;
 }
 
 li > button.link-button {
   padding-bottom: 8px;
   padding-top: 8px;
 }
 
 button:not(.custom-appearance):not(.link-button),
 input[type=button]:not(.custom-appearance),
 input[type=submit]:not(.custom-appearance),
 select {
   margin-bottom: 6px;
   margin-top: 6px;
 }
 
 html[touch-optimized] .tree-item > .tree-row {
   padding: 4px 3px;
 }