We used to calculate hash in completely incorrect way. We use each
forth character to calculate hash but we should use each one.

R=dgozman@chromium.org

Bug: v8:7426
Cq-Include-Trybots: master.tryserver.blink:linux_trusty_blink_rel
Change-Id: Iaaa317bbf3b3ef71632735dfd069db450283b6f4
Reviewed-on: https://chromium-review.googlesource.com/909586
Commit-Queue: Aleksey Kozyatinskiy <kozyatinskiy@chromium.org>
Reviewed-by: Dmitry Gozman <dgozman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#51191}