Add deprecation message in chrome.pushMessaging API

chrome/common/extensions/api/push_messaging.idl

 // Copyright (c) 2012 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.
 
-// Use <code>chrome.pushMessaging</code> to enable apps and extensions to
-// receive message data sent through
+// The <code>chrome.pushMessaging</code> API is currently deprecated, and will
+// no longer be supported soon.
+// Switch to <a href=gcm.html>chrome.gcm API</a> to take advantage of

[not at google - send to devlin, 2014/08/14 22:16:08]

We actually have a [deprecated] annotation that generates code like:

https://developer.chrome.com/extensions/tabs#property-Tab-selected

I'm not sure if it works on namespaces, but it probably should. If not you could
also apply it to getChannelId and onMessage for good measure:

https://code.google.com/p/chromium/codesearch#chromium/src/chrome/common/exte...

[fgorski, 2014/08/20 22:46:47]

Done. 

 // <a href="cloudMessaging.html">Google Cloud Messaging</a>.
 namespace pushMessaging {
 
   dictionary Message {
     // The subchannel the message was sent on;
     // only values 0-3 are valid.
     long subchannelId;
 
     // The payload associated with the message, if any. This should not contain
     // any personally identifiable information.
@@ skipping 17 matching lines @@
     static void getChannelId(optional boolean interactive,
                              ChannelIdCallback callback);
   };
 
   interface Events {
     // Fired when a push message has been received.
     // |message| : The details associated with the message.
     static void onMessage(Message message);
   };
 };