tune SkOpts::hash_fn() quality

We noticed a hash collision scenario we'd like to avoid, and it looks
pretty easy.  The new test failed on my desktop at both asserts,
depending on whether I build 32- or 64-bit, and also on my
CRC-supporting phone.  The Murmur3 path should be fine.

Change-Id: I005de38d68f9b0461536c29e48cf7e5be5caac3e
Reviewed-on: https://skia-review.googlesource.com/c/159621
Commit-Queue: Mike Klein <mtklein@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
Auto-Submit: Mike Klein <mtklein@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
2 files changed