Fix webRequest documentation

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

 <div id="pageData-name" class="pageData">WebRequest API</div>
 
 <!-- BEGIN AUTHORED CONTENT -->
 <p id="classSummary">
 Use the <code>chrome.experimental.webRequest</code> module to intercept, block,
 or modify requests in-flight. This module is still very much experimental. For
 information on how to use experimental APIs, see the
 <a href="experimental.html">chrome.experimental.* APIs</a> page.
 </p>
 
@@ skipping 213 matching lines @@
   {},
   ["blocking"]);
 </pre>
 
 <p>The following example achives the same goal in a more efficient way because
 requests that are not targeted to <code>www.evil.com</code> do not need to be
 passed to the extension:</p>
 <pre>
 chrome.experimental.webRequest.onBeforeRequest.addListener(
   function(details) { return {cancel: true}; },
-  {"*://www.evil.com/*"},
+  {urls: ["*://www.evil.com/*"]},
   ["blocking"]);
 </pre>
 
 <p>The following example illustrates how the User-Agent header can be deleted
 from all requests:</p>
 <pre>
 chrome.experimental.webRequest.onBeforeSendHeaders.addListener(
   function(details) {
     delete details.requestHeaders['User-Agent'];
     return {requestHeaders: details.requestHeaders};
@@ skipping 31 matching lines @@
     // Use the frameUrl e.g. to selectively cancel requests.
     // Attention: The frameUrl can be undefined in some cases. Requests may not
     // originate from a frame (e.g. requests from extensions or shared workers).
   });
 
 chrome.windows.onRemoved.addListener(
   function(windowId) {delete frameUrl[windowId];}
   );
 </pre>
 <!-- END AUTHORED CONTENT -->