Fix array-of-matrix/struct comparisons in Metal.

Metal needs helper functions in order to compare arrays, structs, and
matrices. Depending on the input code, it was possible for the
array-comparison helper to be emitted before a matrix-comparison
or struct-comparison helper. If this occurred, array comparisons of that
matrix or struct type would fail, because the operator== for the array's
inner type was defined after array==, and Metal (like C++) parses
top-to-bottom and only considers functions declared above the current
function.

We now emit prototypes for all the array, struct and matrix helper
function. These prototypes are emitted above any helper functions. This
ensures visibility no matter how your comparisons are organized.

Change-Id: Ib3d8828c301fd0fa6c209788f9ea60800371edbe
Bug: skia:12326
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/437739
Commit-Queue: John Stiles <johnstiles@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
17 files changed