title: Firefox extension not showing icons
body: <p>I have implemented sample mozilla firefox extension to display firefox icon (action button) on toolbar and it will open "<a href="http://www.mozilla.org/" rel="nofollow">http://www.mozilla.org/</a>".
  It is working fine in jpm run, then I have created package of that using jpm xpi and created xpi file. Then I have installed it in my firefox browser and successfully installed but did not work. <strong>It couldn't add firefox icon (action button) on toolbar</strong> (There is no error in console).</p>
  
  <p>Below is the code.</p>
  
  <p><strong>index.js</strong></p>
  
  <p><div class="snippet" data-lang="js" data-hide="false">
  <div class="snippet-code">
  <pre class="snippet-code-js lang-js prettyprint-override"><code>var buttons = require('sdk/ui/button/action');
  var tabs = require("sdk/tabs");
  
  var button = buttons.ActionButton({
    id: "mozilla-link",
    label: "Visit Mozilla",
    icon: {
      "16": "./icon-16.png",
      "32": "./icon-32.png",
      "64": "./icon-64.png"
    },
    onClick: handleClick
  });
  
  function handleClick(state) {
    tabs.open("http://www.mozilla.org/");
  }</code></pre>
  </div>
  </div>
  </p>
  
  <p><strong>package.json</strong></p>
  
  <p><div class="snippet" data-lang="js" data-hide="false">
  <div class="snippet-code">
  <pre class="snippet-code-js lang-js prettyprint-override"><code>{
    "title": "Sample",
    "name": "sample",
    "version": "0.0.1",
    "description": "Sample AddOn",
    "main": "index.js",
    "author": "Sample",
    "engines": {
      "firefox": "&gt;=30.0a1",
      "fennec": "&gt;=30.0a1"
    },
    "license": "MIT"
  }</code></pre>
  </div>
  </div>
  </p>
  
  <p>I have implemented that using - <a href="https://developer.mozilla.org/en-US/Add-ons/SDK/Tutorials/Getting_Started_%28jpm%29" rel="nofollow">https://developer.mozilla.org/en-US/Add-ons/SDK/Tutorials/Getting_Started_%28jpm%29</a></p>
  
  <p>Please Help.</p>
  
  <p>Thanks</p>