Adding a bit of rebustness to SkRectShaderImageFilter

Adding a bit of rebustness to SkRectShaderImageFilter

Since SkRectShaderImageFilter is an image filter, I added logic so that it can actually use the size of an input image as the rect if an empty rect is provided as an argument. I also added logic to prevent creating an empty device.

Committed: https://code.google.com/p/skia/source/detail?r=8739

[Stephen White, 2013-04-17 17:59:39]

https://codereview.chromium.org/14093008/diff/1/src/effects/SkRectShaderImage...
File src/effects/SkRectShaderImageFilter.cpp (right):

https://codereview.chromium.org/14093008/diff/1/src/effects/SkRectShaderImage...
src/effects/SkRectShaderImageFilter.cpp:52: SkBitmap src =
this->getInputResult(0, proxy, source, ctm, loc);
This filter should never have a DAG input, so I'd just avoid getInputResult()
and use source.width() and source.height() directly.

[Stephen White, 2013-04-17 22:28:02]

LGTM

[sugoi1, 2013-04-18 14:13:12]

Committed patchset #2 manually as r8739 (presubmit successful).