Handle dividing by zero in ComputeComplexity

Bug: oss-fuzz:9884
Change-Id: Ibeeb1ffdb46d9a648c7ec8944424af2d0138af59
Reviewed-on: https://skia-review.googlesource.com/156631
Commit-Queue: Yuqian Li <liyuqian@google.com>
Reviewed-by: Mike Klein <mtklein@google.com>
Auto-Submit: Yuqian Li <liyuqian@google.com>
2 files changed