Fix GPU displacement with expanding crop rects.

Fix GPU displacement with expanding crop rects.

Fix GPU displacement with expanding crop rects, and re-enable the
imagefilterscropexpand GM. There were two bugs: the result texture was
being created at input color bitmap size, not the cropped bounds size,
and the matrix in GrContext was not being set to identity before draw.

R=junov@chromium.org

Committed: https://code.google.com/p/skia/source/detail?r=13844

[Stephen White, 2014-03-17 22:05:24]

junov@: PTAL. Thanks!

[Justin Novosad, 2014-03-17 22:08:00]

On 2014/03/17 22:05:24, Stephen White wrote:
> junov@: PTAL. Thanks!

lgtm

[Stephen White, 2014-03-17 23:41:52]

Committed patchset #1 manually as r13844 (presubmit successful).

[epoger, 2014-03-19 21:43:42]

FYI: This CL triggered a strange failure on a single Android buildbot. 

See https://code.google.com/p/skia/issues/detail?id=2313
('Test-Android-Nexus10-MaliT604-Arm7-Release failing comparegms')... I don't
think there's anything you need to do about it, though.

[epoger, 2014-03-21 19:02:30]

A revert of this CL has been created in
https://codereview.chromium.org/208843002/ by epoger@google.com.

The reason for reverting is: Speculative revert (for trybot consumption) per
https://code.google.com/p/skia/issues/detail?id=2313#c13.