tweak conservative bounds value to save aberrant cubic

Bug: 844457
Change-Id: Ia3c7c0592df59022cf04f6747b1fe30975431ea4
Reviewed-on: https://skia-review.googlesource.com/129200
Reviewed-by: Cary Clark <[email protected]>
Commit-Queue: Mike Reed <[email protected]>
2 files changed