[canvaskit] Fix examples and tests of drawPatch and drawVertices

Change-Id: Iab8c085fad220930b838a281834a402f8d96c2af
Bug: skia:12662
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/477437
Reviewed-by: Brian Salomon <bsalomon@google.com>
4 files changed