d3d9/tests: Limit the back buffer to 800x600 in the scissor size test.

[Henri Verbeet]

2009/3/12 Michael Stefaniuc <mstefani at redhat.com>:
> I sent the patch out to provoke a better patch from somebody more
> knowledgeable in that domain. Of course only if it's worth the effort;
> until the advent of the netbooks with their odd screen size assuming
> that 1024x768 will just work was good enough.
>
My EeePC only does 800x640. IIRC test_reset() is affected by a similar
problem, in that it assumes 800x600 is available. I can probably write
a patch that just uses two different screen sizes from the list of
available ones.