chop down huge rects before hairlining

Bug: 826166
Change-Id: I18f4b1dc4f279e37832d4bced0a66b5c356d09c0
Reviewed-on: https://skia-review.googlesource.com/112572
Reviewed-by: Yuqian Li <liyuqian@google.com>
Commit-Queue: Mike Reed <reed@google.com>
(cherry picked from commit c7fbda95404a9422d0dd762d35383d5a61e89440)
Reviewed-on: https://skia-review.googlesource.com/118720
Reviewed-by: Kevin Lubick <kjlubick@google.com>