title: Write text to Clipboard
body: <p>I want to write some text variable into clipboard via Chrome Extension, it will be happened when user presses a short-key. I've done all parts except writing to clipboard.</p>
  
  <p>I've searched entire StackOverflow using these keywords:
  "[google-chrome-extension] Clipboard"</p>
  
  <p>So I want to say, I've seen all related to:</p>
  
  <ul>
  <li>Add <code>clipboardRead</code> and <code>clipboardWrite</code> permission (already done)</li>
  <li>Add text into a <code>&lt;textarea&gt;</code>, call
  <code>document.execCommand('Copy');</code>
  or
  <code>document.execCommand("Copy", false, null);</code></li>
  </ul>
  
  <p>Even I tried my extension on StackOverflow's <code>textarea</code> and I inserted my text into wmd-input part of StackOverflow <code>textarea</code>, then selected it, then called copy. Nothing, nothing, nothing...</p>
  
  <p>Everything tried. Please advise... What am I missing?</p>