Fix flutter roll

Flutter extends from the SkCanvasVirtualEnforcer, so the prior change
to onDrawEdgeAAQuad to accept an SkColor4f instead of SkColor broke
their build, the flutter roller, and--transitively--the G3 roller.

This keeps the old onDrawEdgeAAQuad around as a no-op so their
canvas_spy class can extend from it.

TBR=bsalomon@google.com, stani@google.com

Bug: skia:
Change-Id: I3798ec60a21e90c3d3f5d59f19f7dbe62e37cbec
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/237590
Reviewed-by: Michael Ludwig <michaelludwig@google.com>
Commit-Queue: Michael Ludwig <michaelludwig@google.com>
3 files changed