Move history API out of experimental. Allow extensions to override history page.

chrome/common/extensions/docs/static/experimental.html

 <div id="pageData-name" class="pageData">chrome.experimental.* APIs</div>
 
 <p>
 We'd like your <a href="http://groups.google.com/a/chromium.org/group/chromium-extensions/topics">feedback</a>
 on the following experimental APIs:
 </p>
 
 <ul>
-  <li jsselect="experimentalAPIs();"><a jsvalues=".href: $this + '.html'" jscontent="$this" href="experimental.history.html" js>experimental.history</a></li>
+  <li jsselect="experimentalAPIs();">
+  <a jsvalues=".href: $this + '.html'" jscontent="$this"></a></li>
 </ul>
 
 <p class="caution">
 <b>Caution:</b>
 Don't depend on these experimental APIs.
 They might disappear,
 and they <em>will</em> change.
 Also, the extension gallery doesn't allow you to
 upload extensions that use experimental APIs.
 </p>
@@ skipping 44 matching lines @@
   </li>
 </ol>
 
 <h2 id="other">More information</h2>
 
 <p>
 For information on the standard APIs that extensions can use, see
 <a href="api_index.html">chrome.* APIs</a> and
 <a href="api_other.html">Other APIs</a>.
 </p>