Don't unsubclass the surface's output window if the window has been destroyed.
Don't unsubclass the surface's output window if the window has been destroyed.

Review URL: http://codereview.appspot.com/3357041

git-svn-id: a070b70d2b8c44c266a3870c0cddd9a0ee470458@499 736b8ea6-26fd-11df-bfd4-992fa37f6226

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