Fix for clip assert in Chrome tests

When creating r4798, I overlooked a difference in GrClip and SkClipStack's behaviors. When a clip reduces to a single rect,  GrClip ignores the bounding box passed to it from the SkClipStack and instead uses the reduced rect. A problem arises because the reduced rect is never cropped to the render target's bound. This CL adds another crop to the GrClipData::getConservativeBound helper function.

[reed1, 2012-07-30 17:02:22]

http://codereview.appspot.com/6442063/diff/1/src/gpu/GrClip.cpp
File src/gpu/GrClip.cpp (right):

http://codereview.appspot.com/6442063/diff/1/src/gpu/GrClip.cpp#newcode263
src/gpu/GrClip.cpp:263: // was never trimmed to the render target's bounds.
trivia: MakeWH(w, h) takes 2 fewer arguments

[bsalomon, 2012-07-30 17:06:35]

I confirmed that it fixes the DRT crash. LGTM.

[robertphillips, 2012-07-30 17:11:52]

committed as r4834.