title: Google API Oauth token in firefox webextension
body: <p>I am trying to fetch Oauth2 token for Google Drive API in Firefox Webextension.
  I use background.html to load google Javascript client library. However When  authorize using gapi.auth.authorize is invoked, nothing happens. </p>
  
  <p>My analysis that  "authorize" tries to open new window for User to allow/deny permissions but fails.</p>
  
  <p>Similar thing is achieved in chrome extension with chrome.identity executing in chrome's background.js</p>
  
  <p>Content security policy in manifest.json </p>
  
  <pre><code> "content_security_policy": "script-src 'self' https://apis.google.com; object-src 'self'"
  </code></pre>
  
  <p>Is there any better way to receive Oauth2 token for Google API ? and What am I missing in above approach ?</p>
  
  <p>Thanks.</p>