Use conics with w=Inf to describe triangles for the tessellator

Previously, only the indirect tessellator could draw triangles, and
only with special index data. Using conics with w=Inf will allow us to
draw triangles with the hardware tessellator as well, in addition to
being able to wean the indirect tessellator off an index buffer.

Bug: skia:10419
Bug: chromium:1202607
Change-Id: I180af9cb5410c0e0bb25a2edcfb01e17d4a2f590
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/406977
Commit-Queue: Chris Dalton <csmartdalton@google.com>
Reviewed-by: Michael Ludwig <michaelludwig@google.com>
5 files changed