MD Settings: <settings-dialog>, restore focus effect for the cancel button.

chrome/browser/resources/settings/settings_dialog.html

 <link rel="import" href="chrome://resources/html/polymer.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/iron-icons/iron-icons.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-dialog-behavior/paper-dialog-behavior.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-dialog-behavior/paper-dialog-shared-styles.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-icon-button/paper-icon-button.html">
 
 <dom-module id="settings-dialog">
   <template>
     <style include="paper-dialog-shared-styles"></style>
     <style>
@@ skipping 50 matching lines @@
         -webkit-padding-end: 16px;
         -webkit-padding-start: 16px;
         display: flex;
         justify-content: flex-end;
         margin-bottom: 12px;
       }
 
       :host ::content .button-container .cancel-button {
         -webkit-margin-end: 8px;
         color: var(--paper-grey-600);
+      }
+
+      :host ::content .button-container .cancel-button:not(.keyboard-focus) {

[Dan Beam, 2016/05/03 19:06:27]

i don't think .keyboard-focus is part of the public API; can you use something
that is publicly documented on
https://elements.polymer-project.org/elements/paper-button?  maybe
[aria-pressed] or --paper-button-*-focus?

         font-weight: 500;
       }
 
       :host ::content .footer {
         background-color: var(--paper-grey-200);
         margin: 0;
         padding: 20px;
       }
 
       :host ::content .row {
@@ skipping 27 matching lines @@
         <content select=".body"></content>
         <content select=".button-container"></content>
       </div>
     </div>
     <div class="footer-container">
       <content select=".footer"></content>
     </div>
   </template>
   <script src="settings_dialog.js"></script>
 </dom-module>