Take notification API out of experimental.

chrome/common/extensions/docs/templates/intros/notifications.html

 <table class="intro">
   <tr>
     <th scope="col"></th>
     <th scope="col"></th>
   </tr>
   <tr>
     <td><strong>Description:</strong></td>
     <td>Use the <code>chrome.notifications</code> module
     to create rich notifications using templates and
     show these notifications to users in the system tray
@@ skipping 15 matching lines @@
 
 <p class="warning">
 <b>Warning: </b>
 Currently this API only works on ChromeOS and Windows.
 </p>
 
 <h2 id="usage">Usage</h2>
 
 <p>
 To use this API,
-call the $ref:experimental.notification.create method,
+call the $ref:notifications.create method,
 passing in the notification details
 via the <code>options</code> parameter:
 </p>
 
 <pre>
 chrome.experimental.notification
   .create(id, options, creationCallback);
 </pre>
 
 <p>
-The $ref:experimental.notification.NotificationOptions must include the
-$ref:experimental.notification.TemplateType
+The $ref:notifications.NotificationOptions must include the
+$ref:notifications.TemplateType
 which defines available notification details
 and how those details are displayed.
 All four available template types
 (<code>simple</code>, <code>basic</code>, <code>image</code>, <code>list</code>)
 include the notification <code>title</code> and <code>message</code>.
 </p>
 
 <p>
 They can also include urls to icons or images.
 The <code>simple</code>, <code>basic</code>, and <code>list</code>
@@ skipping 46 matching lines @@
 </p>
 
 <h2 id="events">Listening for and responding to events</h2>
 
 <p>
 With the exception of the <code>simple</code> template,
 all notifications can include event listeners and event handlers
 which respond to user actions.
 For example,
 you can write an event handler to respond to an
-$ref:experimental.notification.onButtonClicked event.
+$ref:notifications.onButtonClicked event.
 </p>
 
 <p>Consider including event listeners and handlers within the
   <a href="app_lifecycle.html#create_event_page">event page</a>,
 so that notifications can pop-up even when the app or extension isn't running.
-</p>
+</p>