Add support for multiple child nodes to SkImageFilters::RuntimeShader

Bug: skia:12766
Change-Id: I9dfe07a71961ab952c1593b9cc68c61191fbc13c
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/489536
Reviewed-by: Michael Ludwig <michaelludwig@google.com>
Reviewed-by: Derek Sollenberger <djsollen@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
4 files changed