Fix Invalid Drawable error when using createWindowContainer on Mac.

You are not supposed to call NSOpenGLContext -setView: for a view that
has not yet called drawRect.  Doing this would result in a invalid
drawable error.

Similar to 4.8 commit cd2a51a66f52767c20e80361033c573651b3a08d

Change-Id: Ibb2300a8c6fe52f786f813987e93d4a3dc145366
Reviewed-by: Gabriel de Dietrich <gabriel.dedietrich@digia.com>