Implement stroking with GPU tessellation

Bootstraps tessellated stroking using GrStrokeGeometry mostly as
written. Strokes get decomposed into tessellation patches that
represent either a "cubic" (single stroked bezier curve with butt
caps) or a "join". The patches get drawn directly to the canvas
without any intermediate stencil steps. For the first revision, only
opaque, constant-color strokes are supported.

Bug: skia:10419
Change-Id: I601289189b93ebdf2f1efecd08628a6e0d9acb01
Reviewed-by: Michael Ludwig <>
Commit-Queue: Chris Dalton <>
9 files changed