Prevent overflow of integral types during constant-folding.

Expressions which would overflow/wrap the result type are now left
as-is.

Change-Id: I6a942f337e6e5761823f5c9dcd214fa58227a626
Bug: skia:10932, skia:12050
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/413138
Auto-Submit: John Stiles <johnstiles@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
6 files changed