[MD settings] adding settings-row class

chrome/browser/resources/settings/settings_page/settings_row.js

+// Copyright 2015 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.
+
+/**
+ * @fileoverview
+ * 'settings-row' shows a row of controls for a setting.  This is used as
+ * a simple container for UI group that is smaller than a page or section,
+ * but larger than a single button or slider.  The row may contain a <left>,
+ * a <right> or both.  Elements withing left or right will be pushed to the
+ * respective ends of the row.
+ *
+ * Examples:
+ *
+ *   <settings-row>
+ *     <left>

[Dan Beam, 2015/10/20 18:31:51]

custom tags should have-dashes

[dschuyler, 2015/10/20 20:46:59]

Ah, I knew about dashes for polymer 
module names - thanks for the tip about
the dashes for all custom tags.

Maybe left-side, right-side

or

Maybe a custom property?  i.e. 
<settings-row>
  <div left>
...

+ *       Press the button
+ *     </left>
+ *     <right>
+ *       <paper-button>THE BUTTON</paper-button>
+ *     </right>
+ *   </settings-row>
+ *
+ * @group Chrome Settings Elements
+ * @element settings-row
+ */
+Polymer({
+  is: 'settings-row',
+});