[svgcanvas] Refactor clipping

Instead of emitting one fully-resolved clip per primitive, build a
clip hierarchy based on SkClipStack genIDs and SVG groups.

Bug: skia:9344
Change-Id: Ic26c7cd2e268a4cc2f251757f0e9e22475fb9994
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/236346
Commit-Queue: Florin Malita <fmalita@chromium.org>
Reviewed-by: Mike Reed <reed@google.com>
2 files changed