title: Chrome extension inject sidebar into page
body: <p>I would like my chrome extension to be able to inject a 300px sidebar on the right side of any page when it is activated.  I am looking for the best way to constrain the entire page to document.body.clientWidth - 300, thereby leaving the 300px on the right for my sidebar.  The sidebar I currently inject is appended to document.body and has a style like so:</p>
  
  <pre><code>width:300px
  position: fixed
  top: 0px
  right: 0px
  height:500px
  </code></pre>
  
  <p>I need a way to prevent the existing page elements from bleeding over into my sidebar.  I was hoping that there would be a way to trick the existing elements into thinking that they were rendering into a browser client 300px narrower than their actual window thereby leaving space for my sidebar but I haven't found any easy way to do so...</p>