Add support for matrix == and != in Metal shaders.

We need to polyfill an operator== and != when these are first
encountered in the code.

Change-Id: I539c838ee1871bcb0c4b66abb8a4a0f91146cd4f
Bug: skia:11306
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/368496
Auto-Submit: John Stiles <johnstiles@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
8 files changed