Besides moving the existing coord-overrides and sample matrix merging
logic on to a shared visitor pattern, this updates the sample coord
reference detection to actually look for references to that built-in.
Previously, we only had this behavior in the CPP code generator. The
.h generator just did a string search for sk_TransformedCoords2D, and
runtime effects just looked at the main signature. Now, the .h generator
is more robust, and runtime effects that declare the main coords parameter
but never use it will not be marked as using the sample coords directly.
Change-Id: I802d610dbda512cf3823c58f349307b3926aa58f
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/299458
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Michael Ludwig <michaelludwig@google.com>
8f3a83671a