[cros] Fix issue with focus stealing when choosing user picture with left/right arrows.

chrome/browser/resources/chromeos/login/oobe_screen_user_image.js

 // Copyright (c) 2011 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 Oobe user image screen implementation.
  */
 
 cr.define('oobe', function() {
   /**
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     userImageList.addEventListener('keydown', function(e) {
       var prevIndex = userImageScreen.selectedUserImage_;
       var len = userImageList.children.length;
       if (e.keyCode == 39 || e.keyCode == 40) {  // right or down
         if (prevIndex < len - 1)
           UserImageScreen.selectUserImage(prevIndex + 1);
       } else if (e.keyCode == 37 || e.keyCode == 38) {  // left or up
         if (prevIndex > 0)
           UserImageScreen.selectUserImage(prevIndex - 1);
       }
+      e.stopPropagation();
     });
   };
 
   /**
    * Selects the specified user image and shows it in preview.
    * @param {number} index The index of the image to select.
    */
   UserImageScreen.selectUserImage = function(index) {
     var userImageList = $('user-image-list');
     var userImageScreen = $('user-image');
     var prevIndex = userImageScreen.selectedUserImage_;
     if (prevIndex != -1) {
       userImageList.children[prevIndex].classList.remove('user-image-selected');
       userImageList.children[prevIndex].setAttribute('tabIndex', '-1');
     }
     if (index != -1) {
       var selectedImage = userImageList.children[index];
       selectedImage.classList.add('user-image-selected');
       selectedImage.setAttribute('tabIndex', '0');
       selectedImage.focus();
       $('user-image-preview').src = selectedImage.src;
     }
     userImageScreen.selectedUserImage_ = index;
   };
 
   return {
     UserImageScreen: UserImageScreen
   };
 });