Enable constant-expression folding at all times.

In some contexts, we rely on constant expressions to fold in order for
SkSL to work properly. (e.g. an array size is allowed to be any
constant-expression in GLSL, but the compiler really needs to know the
actual size). Previously, turning off optimization would break several
tests. Now, constant-expression folding always occurs even when the
optimizer is disabled.

Note that disabling the optimizer isn't an end-user option, so this
only affects internal usage.

Change-Id: I106ecb7e5bff3f7a8235cdccf0a7a60b48a97e2e
Bug: skia:12472
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/469520
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: John Stiles <johnstiles@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
12 files changed