title: unexpected different sizes returned from glGetRenderbufferParameteriv in iOS
body: <p>Hello I am writing an example OpenGLES app, if I setup openGL via the view's <code>initWithCode:(NSCoder *) coder</code> method, the call of
      <code>glGetRenderbufferParameteriv(GL_RENDERBUFFER, GL_RENDERBUFFER_WIDTH, &amp;_backingWidth);</code>
  returns 960x480 for iPad air.</p>
  
  <p>But if I setup openGL in the view's <code>-(void) layoutSubviews</code> method, it will return 2048x1536, </p>
  
  <p>I can not understand why they return different. can any expert explain?</p>