Use 1e-4 rather than 1e-5 as "nonZeroAlpha" in various shader code.

1e-5 may be zero in fp16.


Bug: skia:9099
Change-Id: I28a518f5cf1aa7926f7422625c0f14ed1a082809
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/218558
Commit-Queue: Brian Salomon <bsalomon@google.com>
Auto-Submit: Brian Salomon <bsalomon@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
5 files changed