We should support constant-expressions involving matrices (GLSL ES2
does, WebGL does). We currently don't. We do properly report out-of-
range indexing, but we don't optimize away valid matrix index
expressions or allow matrices to be indexed in a constant-expression
context.
Change-Id: If58aa4c5f15abef421a412957072f3617b4176df
Bug: skia:12472
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/469818
Auto-Submit: John Stiles <johnstiles@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: John Stiles <johnstiles@google.com>
