title: Very simple Chrome Extension to display alert
body: <p>I am trying to create a quick Chrome extension (complete beginner) and just want to display an alert whenever the icon is clicked, so I tried the following:</p>
  
  <p><strong>manifest.json</strong></p>
  
  <pre><code>{
      "name": "Something",
      "version": "1.0",
      "manifest_version": 2,
      "description": "Woohoo",
      "browser_action": {
          "default_icon": "icon.png"
      },
      "content_scripts" : [{
          "matches": ["&lt;all_urls&gt;"],
          "js" : ["bgscript.js"]
      }]
  
  }
  </code></pre>
  
  <p><strong>bgscript.js</strong></p>
  
  <pre><code>chrome.browserAction.onClicked.addListener(function(tab) { 
      alert('icon clicked')
  });
  </code></pre>
  
  <p>However when I click on my icon, nothing happens! Looking at the above - can anyone spot why this wouldn't work?</p>