Remove .html extension from links

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

 <h1>User Authentication</h1>
 
 <p>
 Web authentication protocols utilize HTTP features,
 but Chrome Apps run inside the app container;
 they don’t load over HTTP and can’t perform redirects or set cookies.
 </p>
 
 <p>
-Use the <a href="identity.html">Chrome Identity API</a>
+Use the <a href="identity">Chrome Identity API</a>
 to authenticate users:
 the <code>getAuthToken</code> for users logged into their Google Account and
 the <code>launchWebAuthFlow</code> for users logged into a non-Google account.
 If your app uses its own server to authenticate users, you will need to use the latter.
 </p>
 
 <p class="note">
 <b>API Samples: </b>
 Want to play with the code?
 Check out
@@ skipping 32 matching lines @@
   <li>Get an OAuth2 client ID for your Chrome App.</li>
   <li>Update your manifest to include the client ID and scopes.</li>
   <li>Get the authentication token.</li>
 </ol>
 
 <h3 id="add_permissions">Add permissions and upload app</h3>
 
 <p>
 You need to make sure the identity permission is in your manifest.
 You can then upload your app to the apps and extensions management
-page (see <a href="publish_app.html">Publish</a>).
+page (see <a href="publish_app">Publish</a>).
 </p>
 
 <pre data-filename="manifest.json">
 "permissions": [
   "identity"
 ]
 </pre>
 
 <h3 id="copy_key">Copy key to your manifest</h3>
 
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 </p>
 
 <p>
 The best practice we suggest is to use silent mode
 when there is no user gesture involved and use interactive mode
 if there is a user gesture (for example, the user clicked the Sign In button in your app).
 Note that we do not enforce gesture requirement.
 </p>
 
 <p class="backtotop"><a href="#top">Back to top</a></p>