Fix some typos, broken links and other issues in extension docs

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

 <h1 class="page_title">chrome.experimental.* APIs</h1>
 {{^is_apps}}
 <div class="doc-family extensions">
 <p>
 Before you start, <strong>choose the right version of this page.</strong>
 You should read either:
 </p>
 
 <ul>
   <li> <a href="http://code.google.com/chrome/extensions/trunk/experimental.html">Most recent experimental APIs</a>
@@ skipping 70 matching lines @@
   </li>
   <li class="doc-family extensions">
     Using either the
     <a href="http://code.google.com/chrome/extensions/trunk/experimental.html">most recent API documentation</a> (if you're using Canary) or the
     <a href="http://code.google.com/chrome/extensions/dev/experimental.html">API documentation for the Dev channel</a>,
     write the code for your extension.
   </li>
   {{/is_apps}}
   <li>
     Specify the "experimental"
-    <a href="manifest.html#permissions">permission</a>
+    <a href="declare_permissions.html">permission</a>
     in your manifest, like this:
 <pre>
 "permissions": [
   <b>"experimental"</b>,
   ...
 ],
 </pre>
   </li>
   <li>
     Enable the experimental API in your browser.
@@ skipping 29 matching lines @@
   {{/is_apps}}
 </ol>
 
 <h2 id="other">More APIs</h2>
 
 <p>
 For information on the standard APIs, see
 <a href="api_index.html">chrome.* APIs</a> and
 <a href="api_other.html">Other APIs</a>.
 </p>