title: Set firefox profile with protractor
body: <p>I want to run tests with Firefox/protractor with the cache feature disabled.
  (Actually, I'm trying to prevent 304 HTTP responses).</p>
  
  <p>There are multiple ways to do this:</p>
  
  <ul>
  <li>Disable the cache from the backend-side by droping Etag headers -> I can't modify the backend</li>
  <li>Drop the Etag header from the frontend-side -> I tried, it did not work</li>
  <li>Disable the cache from firefox: I just have to set the flag <code>network.http.use-cache</code> to false</li>
  </ul>
  
  <p>Manually it works. I receive only 200 responses and it's great.
  I want to be able to set this flag through protractor configuration. After some search I found out that I had to create a custom profile and set it in protractor this way (<a href="https://code.google.com/p/selenium/wiki/DesiredCapabilities" rel="noreferrer">https://code.google.com/p/selenium/wiki/DesiredCapabilities</a>):</p>
  
  <pre><code>capabilities: {
     browserName: 'firefox',
     firefox_profile: 'support/firefox_profile'
   }
  </code></pre>
  
  <p>The problem is that the firefox profile is not considered. Is it the right option?
  Do you have a better idea?</p>
  
  <p>Thanks for your help.</p>
  
  <p>EDIT:
  As someone (suggested</p>
  
  <pre><code>capabilities: {
    prefs: {
      'config.http.use-cache': false
    }
  }
  </code></pre>
  
  <p>It did not work - I checked in about:config, the flag was still enabled.
  How do you know what options you can pass in the capabilities?</p>