CCPR: Avoid left shifts on negative numbers

(ASAN doesn't like them.)

Bug: skia:
Change-Id: Id28d3ea9cabc9895cb097eae3e437f557178fe1c
Reviewed-on: https://skia-review.googlesource.com/54180
Commit-Queue: Chris Dalton <csmartdalton@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
1 file changed