cros: Lock Screen: Fixed an issue with tab order on the lock screen.

chrome/browser/resources/chromeos/quick_unlock/pin_keyboard.html

 <!-- TODO(crbug.com/603217): Use i18n instead of string literals. Figure out
                              what i18n to use for keypad, ie, does 1 ABC make
                              sense in every scenario? -->
 
 <link rel="import" href="chrome://resources/cr_elements/icons.html">
 <link rel="import" href="chrome://resources/html/i18n_behavior.html">
 <link rel="import" href="chrome://resources/html/polymer.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-button/paper-button.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-icon-button/paper-icon-button.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-styles/color.html">
@@ skipping 14 matching lines @@
       <g id="backspace">
         <path d="M22 3H7c-.69 0-1.23.35-1.59.88L0 12l5.41 8.11c.36.53.9.89 1.59.89h15c1.1 0 2-.9 2-2V5c0-1.1-.9-2-2-2zm-3 12.59L17.59 17 14 13.41 10.41 17 9 15.59 12.59 12 9 8.41 10.41 7 14 10.59 17.59 7 19 8.41 15.41 12 19 15.59z">
       </g>
     </defs>
   </svg>
 </iron-iconset-svg>
 
 <dom-module id="pin-keyboard">
   <template>
     <style>
+      :host {
+        outline: none;
+      }
+
       #root {
         direction: ltr;
         display: flex;
       }
 
       .row {
         display: flex;
       }
 
       .digit-button {
@@ skipping 200 matching lines @@
                                noink>
             </paper-icon-button>
             <paper-ripple>
           </div>
         </div>
       </div>
     </div>
   </template>
   <script src="pin_keyboard.js"></script>
 </dom-module>