title: Loader onStartLoading method is not abstract
body: <p>I just Have a question.
  Why 
  <code>protected void onStartLoading() {}</code> in Loader is not abstract and has empty body because without implementing it in your loader <code>loadInBackground()</code> wont be started except if you call <code>forceLoad()</code>.
  I believe it should be abstract, but maybe there are any reasons why it is not.</p>