Finds the (octagonal) intersection of the path's bounding octagon and
the scissor, and draws that octagon instead. This allows us to avoid
ever using the scissor when drawing paths to the main canvas. It will
also let us use that same octagon without scissor when resolving the
stencil buffer to coverage in MSAA mode.
Bug: skia:
Change-Id: Ia7fe60343424bc77532fa9919d3fa108337a5d63
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/212840
Commit-Queue: Chris Dalton <csmartdalton@google.com>
Reviewed-by: Robert Phillips <robertphillips@google.com>
