[sksg] Refactor gradient implementation
Currently, gradients are PaintNode subclasses - which limits their
applicability to leaf DAG nodes.
In order to support generalized gradient/shader effects:
* introduce a new Shader base class
* refactor gradients as Shader subclasses
* introduce ShaderPaint (to support current Gradient-as-paint use)
* introduce ShaderEffect (to support future Gradient-as-effect use)
Tangentially:
* rename SkSGPaintNode.h -> SkSGPaint.h
* consolidate sksg::Color into SkSGPaint.h
Change-Id: I94ba949f4504c09cfde4a4f030d927411fdd66a2
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/205263
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Florin Malita <fmalita@chromium.org>
26 files changed