Optimize GrTessellatePathOp's code to emit inner triangles

Previously we used a naive algorithm to generate "middle-out" topologies
for inner polygons, including copying all endpoints to a new array.

This CL adds a "GrMiddleOutPolygonTriangulator" class that
accomplishes the same thing in 1/5th the time using a small O(log N)
stack.

Change-Id: I3a7059e5d133a730b7084a17d8fbaaa3aaa81336
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/285531
Commit-Queue: Chris Dalton <csmartdalton@google.com>
Reviewed-by: Michael Ludwig <michaelludwig@google.com>
6 files changed