title: No ActionBar in PreferenceActivity after upgrade to Support Library v21
body: <p>After I upgraded to the Support Library v21 my ActionBar in my <a href="http://developer.android.com/reference/android/preference/PreferenceActivity.html" rel="noreferrer"><code>PreferenceActivity</code></a> is gone.</p>
  
  <p>Did I miss some attributes in my theme to activate it again? I had some similar trouble with <a href="https://stackoverflow.com/q/26506751/995926">a black ActionBar</a>.</p>
  
  <p>I also tried to add it a little hackish by adding a <a href="http://developer.android.com/reference/android/support/v7/widget/Toolbar.html" rel="noreferrer"><code>Toolbar</code></a> to the root layout, but that did not work as expected.</p>