Remove .html extension from links

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

 <h1>External Content</h1>
 
 
 <p>
-The <a href="app_architecture.html#security">Chrome Apps security model</a> disallows
+The <a href="app_architecture#security">Chrome Apps security model</a> disallows
 external content in iframes and
 the use of inline scripting and <code>eval()</code>.
 You can override these restrictions,
 but your external content must be isolated from the app.
 </p>
 
 <p>
 Isolated content cannot directly
 access the app's data or any of the APIs.
 Use cross-origin XMLHttpRequests
 and post-messaging to communicate between the event page and sandboxed content
 and indirectly access the APIs.
 </p>
 
 <p class="note">
 <b>API Sample: </b>
 Want to play with the code?
 Check out the
 <a href="https://github.com/GoogleChrome/chrome-app-samples/tree/master/sandbox">sandbox</a> sample.
 </p>
 
 <h2 id="external">Referencing external resources</h2>
 
 <p>
-The <a href="contentSecurityPolicy.html">Content Security Policy</a> used by apps disallows
+The <a href="contentSecurityPolicy">Content Security Policy</a> used by apps disallows
 the use of many kinds of remote URLs, so you can't directly reference external
 images, stylesheets, or fonts from an app page. Instead, you can use use
 cross-origin XMLHttpRequests to fetch these resources,
 and then serve them via <code>blob:</code> URLs.
 </p>
 
 <h3 id="manifest">Manifest requirement</h3>
 
 <p>
 To be able to do cross-origin XMLHttpRequests, you'll need to add a permission
@@ skipping 20 matching lines @@
 xhr.responseType = 'blob';
 xhr.onload = function(e) {
   var img = document.createElement('img');
   img.src = window.URL.createObjectURL(this.response);
   document.body.appendChild(img);
 };
 
 xhr.send();
 </pre>
 
-<p>You may want to <a href="offline_apps.html#saving-locally">save</a>
+<p>You may want to <a href="offline_apps#saving-locally">save</a>
 these resources locally, so that they are available offline.</p>
 
 <h2 id="webview">Embed external web pages</h2>
 
 <p class="note">
 <b>API Sample: </b>
 Want to play with the code? Check out the
 <a href="https://github.com/GoogleChrome/chrome-app-samples/tree/master/browser">browser</a>
 sample.
 </p>
@@ skipping 38 matching lines @@
 
 <h2 id="sandboxing">Sandbox local content</h2>
 
 <p>
 Sandboxing allows specified pages
 to be served in a sandboxed, unique origin.
 These pages are then exempt from their Content Security Policy.
 Sandboxed pages can use iframes, inline scripting,
 and <code>eval()</code>.
 Check out the manifest field description for
-<a href="manifest/sandbox.html">sandbox</a>.
+<a href="manifest/sandbox">sandbox</a>.
 </p>
 
 <p>
 It's a trade-off though:
 sandboxed pages can't use the chrome.* APIs.
 If you need to do things like <code>eval()</code>,
 go this route to be exempt from CSP,
 but you won't be able to use the cool new stuff.
 </p>
 
@@ skipping 147 matching lines @@
 
 <pre data-filename="sandboxed.html">
 var messageHandler = function(e) {
   console.log('Background script says hello.', e.data);
 };
 
 window.addEventListener('message', messageHandler);
 </pre>
 
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