TRAC #14054
The SetRenderTarget calls used in Blit::boxFilter() and Surface::swap() implicitly reset the scissor and viewport rectangles. So we need to ensure that the original rectangles get captured, and restored afterwards (the Context only keeps track of explicitly changed state).
Signed-off-by: Daniel Koch

git-svn-id: https://angleproject.googlecode.com/svn/trunk@472 736b8ea6-26fd-11df-bfd4-992fa37f6226