Fix GPU colormatrix color filter with saturated alpha.

Clamp RGBA values before unpremultiplying, to match the raster path. This causes a problem when the resulting
alpha is >1.0, resulting in overly saturated RGB.

Covered by the setYUV2RGB() test case in the colormatrix GM.

R=bsalomon@google.com

Review URL: https://codereview.chromium.org/196133006

git-svn-id: http://skia.googlecode.com/svn/trunk@13778 2bbb7eff-a529-9590-31e7-b0007b416f81
2 files changed