title: Setting subview's width equal to window width on launch
body: <p>I'm struggling getting a subview (which is acting as a custom toolbar [I need a <code>NSView</code> rather than an <code>NSToolbar</code>]) centred within an <code>INAppStoreWindow</code>..</p>
  
  <p>The subview is being added correctly, and stretches correctly <em>only if the window is exactly the same width as the custom view that I've created in IB</em>.</p>
  
  <p>If the window opens wider than the custom view, it does not stretch properly. The window seems to open in exactly the same state as I left it (in Lion), which therefore means I have to set the width of the custom view to the restored window width  on launch.</p>
  
  <p>It's also important that the buttons etc I have placed in the centre of the view in the nib remain centred...</p>
  
  <p>How do I do this?</p>
  
  <p>Edit: to make this clear, <strong>how do I get a restored window's width? I have set it to 480 in the nib file but if I resize the window, quit then restart the app, <code>window.frame.size.width</code> still returns 480, not the width I quit with..</strong></p>
  
  <p>Many thanks</p>