Add deprecation message in chrome.pushMessaging API

chrome/common/extensions/docs/templates/articles/cloudMessagingV1.html

 <meta name="doc-family" content="apps">
 <h1>Google Cloud Messaging for Chrome V1</h1>
 
 <p class="note">
-Google Cloud Messaging for Chrome V1 will be legacy soon.
-Use the new <a href="cloudMessaging">Google Cloud Messaging API</a>.
+Google Cloud Messaging for Chrome V1 is deprecated since Chrome 38.
+It will be removed in Chrome 40.
+Use the new <a href="cloudMessaging">Google Cloud Messaging</a>.
 </p>
 
 <p>
 Google Cloud Messaging for Chrome (GCM) is a service
 for signed-in Chrome users
 that helps developers send message data from servers
 to their Chrome apps and extensions.
 The service is intended to wake up an app or extension,
 and/or alert a user.
 For example, calendar updates could be pushed to users
@@ skipping 92 matching lines @@
 </p>
 
 <ol>
   <li>Register your app or extension:
     <ul>
       <li>Create the client ID in the Google APIs Console.</li>
       <li>Get the refresh token to set up authorization to use the service.</li>
     </ul>
   </li>
   <li>Set up your app or extension to use the service:
-        <ul>
-          <li>Add the permission to the manifest.</li>
-          <li>Include a call to <code>getChannelId</code>
-      for any user who is to receive a message.</li>
-          <li>Register a handler to receive the
-          <code>onMessage</code> event.</li>    
-        </ul>
-   </li>
+    <ul>
+      <li>Add the permission to the manifest.</li>
+      <li>Include a call to <code>getChannelId</code>
+        for any user who is to receive a message.</li>
+      <li>Register a handler to receive the <code>onMessage</code> event.</li>
+    </ul>
+  </li>
   <li>Publish your app in the Chrome Web Store. </li>
   <li>Use refresh token to get a valid access token.</li>
   <li>Send message to user.</li>
 </ol>
 
 <h2 id="two">Register app or extension</h2>
 
 <h3 id="clientid">Create client ID</h3>
 
 <p>
@@ skipping 411 matching lines @@
 you need to remove the key because the Store does not currently allow manifests
 with keys.
 </p>
 
 <h2 id="feedback">Feedback</h2>
 
 <p>You can provide feedback about Google Cloud Messaging
 and the pushMessaging API through the Google Group
 <a target="_blank" href="https://groups.google.com/forum/#!forum/gcm-for-chrome-feedback">GCM for Chrome feedback</a>.
 Use this group to ask for help, file bug reports, and request features.</p>