Example of usage of new features of context and screen.

chrome/browser/resources/login/screen.js

 // Copyright 2014 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 Base class for all login WebUI screens.
  */
 cr.define('login', function() {
   var Screen = cr.ui.define('div');
 
@@ skipping 36 matching lines @@
 
     /**
      * Sends message to Chrome, adding needed prefix to message name. All
      * arguments after |messageName| are packed into message parameters list.
      *
      * @param {string} messageName Name of message without a prefix.
      * @param {...*} varArgs parameters for message.
      */
     send: function(messageName, varArgs) {
       if (arguments.length == 0)
-        throw Error('Message name is not provided.');
+        throw Error("Message name is not provided.");
       var fullMessageName = this.sendPrefix_ + messageName;
       var payload = Array.prototype.slice.call(arguments, 1);
       chrome.send(fullMessageName, payload);
     },
 
     decorate: doNothing,
 
     /**
      * Returns minimal size that screen prefers to have. Default implementation
      * returns current screen size.
@@ skipping 152 matching lines @@
                 return screen[x].apply(screen, arguments);
               };
             })(propertyName);
           }
         });
         constructor.contextChanged = function() {
           var screen = $(id);
           screen.contextChanged_.apply(screen, arguments);
         }
         constructor.prototype.name = function() { return id; };
+        constructor.prototype.sendPrefix_ = 'login.' + name + '.';
 
         constructor.register = function() {
           var screen = $(id);
           constructor.decorate(screen);
           Oobe.getInstance().registerScreen(screen);
         };
 
         var result = {};
         result[name] = constructor;
         return result;
       });
     }
   };
 });