Add wireframe support to Metal.

Also fixes segfault with cached shaders.

Change-Id: I32be8c3dd28e93ffabc61437e62be729e4fc2d32
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/261085
Commit-Queue: Jim Van Verth <jvanverth@google.com>
Reviewed-by: Chris Dalton <csmartdalton@google.com>
2 files changed