[gm] Add GMs that apply a gradient to a path

Add two gradient shader GMs that apply the shader paint to a Bezier
curve. This is to test the correctness of atlas path renders.

Bug: b/280927575
Change-Id: I63bc0bc568dc1c2cdade49d7837b1c37653041a4
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/712677
Reviewed-by: Brian Osman <brianosman@google.com>
Reviewed-by: Michael Ludwig <michaelludwig@google.com>
Commit-Queue: Arman Uguray <armansito@google.com>
3 files changed