Add deprecation message in chrome.pushMessaging API

chrome/common/extensions/api/push_messaging.idl

Index: chrome/common/extensions/api/push_messaging.idl
diff --git a/chrome/common/extensions/api/push_messaging.idl b/chrome/common/extensions/api/push_messaging.idl
index 0f6917542248db1a813fd7b91b7a668a333b924d..5499ab13e3ec78736e3d594c5c8e1d9325f4d252 100644
--- a/chrome/common/extensions/api/push_messaging.idl
+++ b/chrome/common/extensions/api/push_messaging.idl
@@ -2,8 +2,9 @@
 // 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 {