ccpr: Don't solve for cubic roots that are out of range

Most real-world cubics don't have both KLM roots inside T=0..1, and a
large amount don't have any. This CL gives a nice speedup by not
wasting time finding padding around KLM roots that we aren't going to
chop at anyway.

Bug: skia:
Change-Id: Icb7217142e29fc3f8e8ff657e9dc739caf6d6714
Reviewed-on: https://skia-review.googlesource.com/122129
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Chris Dalton <csmartdalton@google.com>
1 file changed