title: "chrome.tabs.create" works, but "chrome.tabs.update" doesn't
body: <pre><code>function doit() {
   alert(3);
   // Statement 1
   // chrome.tabs.create({url:"http://www.google.com"});
   // Statement 2
   // chrome.tabs.update({url:"http://en.wikipedia.org"});
   alert(4);
  }
  
  
  chrome.browserAction.onClicked.addListener(doit);
  </code></pre>
  
  <hr>
  
  <p>When the script runs as is, I get JS alerts of 3 and 4.  OK.</p>
  
  <p>When I comment in statement 1 and run the script, I get a JS alert of 3, then
  Google opens in a new, active tab, then I get a JS alert of 4.  As expected.</p>
  
  <p>When I comment out statement 1 and comment in statement 2, I get a JS alert of 3, 
  and that's it.  </p>
  
  <p>According to <a href="http://code.google.com/chrome/extensions/tabs.html#method-update" rel="noreferrer">http://code.google.com/chrome/extensions/tabs.html#method-update</a>, 
  I do not need to pass a tabId object, because it "defaults to the selected tab of the current window." The url object is defined as "A URL to navigate the tab to", as I noticed
  when I ran the chrome.tabs.create in statement 1.  </p>
  
  <p>Why does my chrome.tabs.update statement not work?</p>