Add function to GrDataUtils to handle color conversions.

Like SkConvertPixels but knows about all GrColorTypes, origin, and can
apply an arbitrary GrSwizzle.

Use in GrSurfaceContext read/write pixels methods.

Add support for '0' to GrSwizzle.


Change-Id: Ib9dd215fcb0ee8b33c4020893c22b4ab7ce1f40b
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/220761
Commit-Queue: Brian Salomon <bsalomon@google.com>
Reviewed-by: Greg Daniel <egdaniel@google.com>
14 files changed