Allow child effects in SkMeshSpecification.

Programs can now create an SkMeshSpecification even if its fragment
program references a child effect. However, SkMesh does not support
child effects yet, and attempting to pass a mesh specification to
SkMesh::Make that includes a child effect will currently result in
an error.

Bug: b/40045302
Change-Id: I9a153a8635685e27b0faa2b1d8eee621a1d1d08f
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/759269
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: John Stiles <johnstiles@google.com>
4 files changed