Remove .html extension from links

chrome/common/extensions/docs/templates/articles/cloudMessagingV2.html

 <meta name="doc-family" content="apps">
 <h1 id="gcm">Google Cloud Messaging</h1>
 
 <p>Google Cloud Messaging (GCM) is a service for both Android-powered device and
-Chrome instances to send and receive message data from servers. <a href="gcm.html">GCM Chrome
+Chrome instances to send and receive message data from servers. <a href="gcm">GCM Chrome
 API</a> allows the Chrome apps or extensions to access the GCM
 service for the signed-in Chrome users. The service works even if an app or
 extension isn't currently running. For example, calendar updates could be pushed
 to users even when their calendar app isn't open. </p>
 
 <p>To use both API and service, you must agree to the <a href="https://developers.google.com/terms/">Google APIs Terms of
 Service</a> and <a href="https://developers.google.com/cloud/terms/">Google Cloud Platform Terms
 of Service</a>.</p>
 
 <p>This document describes how to set up and use GCM. For additional information
-see the reference documentation for the <a href="gcm.html">GCM Chrome API</a> and
+see the reference documentation for the <a href="gcm">GCM Chrome API</a> and
 the <a href="http://developer.android.com/google/gcm/index.html">GCM Service</a>. To get
 help with GCM or to give us feedback, please see
 <a href="#feedback">Feedback</a>.</p>
 
 <p>Please note that GCM Chrome API is experimental. It is only available to Chrome
 users on the dev channel.</p>
 
 <p class="note"><strong>API Samples</strong>: Want to play with the code? Check out the
 <a href="https://github.com/GoogleChrome/chrome-app-samples/tree/master/gcm-notifications">gcm-notifications</a>
 sample.</p>
@@ skipping 87 matching lines @@
 <code>manifest.json</code>.</p>
 
 <pre data-filename="manifest.json"><code>
 "permissions": [
   "gcm", "storage", ...
 ]
 </code></pre>
 
 <p>Please note that the <code>storage</code> permission is also provided here because the
 sample codes below needs to persist some data via the
-<a href="storage.html">chrome.storage</a> API.</p>
+<a href="storage">chrome.storage</a> API.</p>
 
 <h2 id="write_chrome_app_or_extension">Write Chrome App or Extension</h2>
 
 <h3 id="obtain_registration_id">Obtain registration ID</h3>
 
 <p>Your app or extension needs to register with GCM servers before it can receive
 messages. When an app or extension registers, it receives a registration ID.
 This is achieved by calling $(ref:gcm.register) and specifying a list of senders
 identified by project numbers from Google Developers Console. Your app or
 extension should pass a callback function to verify that the registration was
@@ skipping 92 matching lines @@
 <p>To send messages upstream, your app or extension should call $(ref:gcm.send) with an
 object containing:</p>
 
 <ul>
 <li>Message ID that identifies the message when it fails to be queued or
 delivered. The message ID can be any kind of string. However, it is
 recommended to stay unique across the lifetime of your app or extension, even
 after it restarts. If you use the same message ID, there may be a chance that
 the previous message gets overridden. If an auto-increment counter is used to
 create the message ID, your app or extension should persist the counter value
-via <a href="storage.html">chrome.storage</a> API and restore it when the app
+via <a href="storage">chrome.storage</a> API and restore it when the app
 reloads.</li>
 <li>Destination ID that identifies the server. This is the project number from the
 Google Developers Console plus the suffix "@gcm.googleapis.com".</li>
 <li>Data that consist of a list of string-to-string key value pairs (up to 4KB
 total).</li>
 <li>Time-to-live (TTL, optional). This property value must be a duration from 0 to
 2,419,200 seconds (4 weeks) and it corresponds to the maximum period of time
 for which GCM will store and try to deliver the message. If this property is
 not set, it is default to the maximum value. When a TTL is set to 0, GCM will
 try to deliver the message immediately. If the immediate effort fails, the
@@ skipping 122 matching lines @@
 <li><strong>Unknown error occurred</strong>: this could happen due to any other internal
 errors.</li>
 </ul>
 
 <h2 id="feedback">Feedback</h2>
 
 <p>You can provide feedback about Google Cloud Messaging and the gcm API through
 the Google Group <a 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>