Remove GrColorSpaceXform from GrGradientEffect

Use a local xform to convert color stops for analytic gradients.
For texture-based gradients, wrap the FP with an xform effect.
To simplify this code, add a new AdjustFP helper to do the color
xform, and also add the MulOutputByInputAlpha stage.

Bug: skia:
Change-Id: Icde19b5ec1c66aae76f894e9978c90a5f00c852e
Reviewed-on: https://skia-review.googlesource.com/62500
Reviewed-by: Florin Malita <fmalita@chromium.org>
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
7 files changed