Fix for loops with multiple init-variables in Metal.

This is structured differently than the GLSL fix, due to the different
semantics of array-types in Metal.

Change-Id: I27ad11539bbbb96abb0686d5686b8fcd2f5dd6d1
Bug: skia:11860
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/396916
Commit-Queue: John Stiles <johnstiles@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
Reviewed-by: Ethan Nicholas <ethannicholas@google.com>
2 files changed