Add 8888 fast SrcOver mode.

The SkLinearBitmapPipeline_tile change is an edge case fix.

This will not function until gDefaultProfileSRGB in SkImageInfo is set to true.

The srcover implementation is not the fastest, and I'm working on a better version.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1886233006

Review-Url: https://codereview.chromium.org/1886233006
3 files changed