Keep paint color range/precision into ops and GPs (using GrColor4h)

We still degrade to bytes when creating vertices (tagged TODO4F).

Note: Guarded for Chrome (by making GrColor4h a wrapper around
GrColor).

Bug: skia:
Change-Id: Id8a1d9eec7978d52b059cd9952666bc1217ee073
Reviewed-on: https://skia-review.googlesource.com/c/165527
Commit-Queue: Brian Osman <brianosman@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
51 files changed