We now clearly differentiate between:
- unseeded hash for 32-bit integers
- unseeded hash for 64-bit integers
- seeded hash for 32-bit integers
- seeded hash for strings


R=bmeurer@chromium.org

Bug: chromium:680662
Change-Id: I7459958c4158ee3501c962943dff8f33258bb5ce
Reviewed-on: https://chromium-review.googlesource.com/1235973
Commit-Queue: Yang Guo <yangguo@chromium.org>
Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#56068}