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

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

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 }
 
 #pics td {
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   width:50%!important;
   border:none;
   padding:0 1em;
   font-size:90%;
 }
 
 #pics img {
   width:188;
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 <div id="pageData-title" class="pageData">Override Pages</div>
 <div id="pageData-showTOC" class="pageData">true</div>
 
 <p>
 Override pages are a way to replace a page
 that Google Chrome provides
 with an HTML file that your extension provides.
 An override page usually has CSS and JavaScript code,
-in addition to HTML.
+in addition to HTML.  A single extension can only override 
+one page.
 </p>
 
 <p>
-Currently, the only page you can replace is
-the <em>New Tab page</em> &mdash;
-the page that appears
-when the user creates a new tab or window.
+Currently, extensions can replace two pages:
+<ul>
+  <li> The <em>New Tab page</em> &mdash;
+  the page that appears when the user creates a new tab or window.</li>
+
+  <li> The <em>History page</em> &mdash; 
+  the page that appears when the user selects the 'History' menu item.</li>
+</ul>
 </p>
-
 <table id="pics">
   <tr>
     <td> <b>The default New Tab page</b> </td>
     <td> <b>An alternative New Tab page</b> </td>
   </tr>
   <tr>
     <td>
       <img src="images/ntp-default.png"
         alt="default New Tab page"
         width="200" height="173">
     </td>
     <td>
       <img src="images/ntp-blank.png"
         alt="a blank New Tab page"
         width="200" height="173">
     </td>
   </tr>
 </table>
 
-
 <h2 id="manifest">Manifest</h2>
 
 <p>
-Register your New Tab page in the
+Register override pages in the
 <a href="manifest.html">extension manifest</a>
-like this:
+using property <code>chrome_url_overrides</code>.  For example, the new tabs page can be overridden like this:
 </p>
 
 <pre>{
   "name": "My extension",
   ...
   <b>"chrome_url_overrides": {
     "newtab": "newtab.html"
   }</b>,
   ...
 }</pre>
 
+You can override the history page like this:
+
+<pre>{
+  "name": "My extension",
+  ...
+  <b>"chrome_url_overrides": {
+    "history": "history.html"
+  }</b>,
+  ...
+}</pre>
+
+A single extension may only override one page.
+
 <h2 id="tips">Tips</h2>
 
 <p>
-For an effective New Tab page, follow these guidelines:
+For an effective override pages, follow these guidelines:
 </p>
 
 <ul>
   <li>
     <p>
     <b>Make your page quick and small.</b> <br />
-    Because the New Tab page appears often,
-    its performance is important.
+    Users expect built in browser pages to open instantly.  Avoid doing things that 
+    may take a long time.
     For example, avoid synchronous fetches of network or database resources.
     </p>
   </li>
   <li>
     <p>
     <b>Include a title in your page.</b> <br />
     Otherwise people will see the URL of the page,
     which might confuse them.
     Here's an example of specifying the title:
     <code>&lt;title>New&nbsp;Tab&lt;/title></code>
     </p>
 
   <li>
     <p>
     <b>Don't rely on the page having the keyboard focus.</b> <br />
     The address bar always gets the focus first
     when the user creates a new tab.
     </p>
   </li>
   <li>
     <p>
-    <b>Don't try to emulate the default New Tab page.</b> <br />
+    <b>Don't try to emulate the default pages.</b> <br />
     The APIs necessary to create
     a slightly modified version of the default New Tab page &mdash;
     with top pages,
     recently closed pages,
     tips,
     a theme background image,
     and so on &mdash;
     don't exist yet.
     Until they do,
     you're better off trying to make something completely different.
     </p>
   </li>
 </ul>
 
 <h2 id="examples"> Examples </h2>
 
 <p>
 You can find simple examples of defining override pages in the
 <a href="http://src.chromium.org/viewvc/chrome/trunk/src/chrome/common/extensions/docs/examples/api/override/">examples/api/override</a>
 directory.
 For other examples and for help in viewing the source code, see
 <a href="samples.html">Samples</a>.
 </p>
 
 
 <!-- [PENDING: Maybe have a gallery of NTPs?] -->