title: setInterval to reload page google chrome extension
body: <p>I have code background js:</p>
  
  <pre><code>chrome.contextMenus.onClicked.addListener(function(tab) {
      chrome.tabs.executeScript(null, {
          code: "setInterval(function(){alert('test')}, 2000)"
      });
  });
  
  var id = chrome.contextMenus.create({
      "title": "Auto Refresh",
      "contexts": ["page"]
  });​
  </code></pre>
  
  <p>It works, each 2 seconds it have a alert box "test";</p>
  
  <p>But I replace alert('test') by location.reload:</p>
  
  <pre><code>chrome.contextMenus.onClicked.addListener(function(tab) {
      chrome.tabs.executeScript(null, {
          code: "setInterval(function(){location.reload()}, 2000)"
      });
  });
  
  var id = chrome.contextMenus.create({
      "title": "Auto Refresh",
      "contexts": ["page"]
  });​
  </code></pre>
  
  <p>It only have 1 refresh for the first time and don't continue to refresh. Please help me, thanks</p>