title: setSystemUiVisibility(SYSTEM_UI_FLAG_LAYOUT_HIDE_NAVIGATION) does not work
body: <p>I've been battling with setSystemUiVisibility() to try to hide the soft navigation buttons for a while (for a video player). It does not seem to work as advertised. Here is my code, inside a visible <code>FrameLayout</code>.</p>
  
  <pre><code>void setNavVisibility(boolean visible)
  {
      int newVis = SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN;
      if (!visible)
      {
          newVis |= SYSTEM_UI_FLAG_LOW_PROFILE | SYSTEM_UI_FLAG_HIDE_NAVIGATION;
      }
      setSystemUiVisibility(newVis);
  }
  </code></pre>
  
  <p>Slightly modified from the SDK example:</p>
  
  <pre><code>    void setNavVisibility(boolean visible) {
          int newVis = SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN
                  | SYSTEM_UI_FLAG_LAYOUT_HIDE_NAVIGATION
                  | SYSTEM_UI_FLAG_LAYOUT_STABLE;
          if (!visible) {
              newVis |= SYSTEM_UI_FLAG_LOW_PROFILE | SYSTEM_UI_FLAG_FULLSCREEN
                      | SYSTEM_UI_FLAG_HIDE_NAVIGATION;
          }
  </code></pre>
  
  <p>Neither do anything when called. I had some success when I called them from a different <code>View</code>, but the documentation doesn't mention that the <code>View</code> you are calling from has any effect? I assume that the documentation is (surprise surprise) somewhat lacking here. Does anyone know what's really going on?</p>