Fix dimensions and color-spin in color4shader GM

BUG=skia:

GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=3907

Change-Id: I0f263d98f942eda07eec4dabfec484461f77f83d
Reviewed-on: https://skia-review.googlesource.com/3907
Reviewed-by: Matt Sarett <msarett@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
1 file changed