This is so that we can distinguish hash tables by instance type. We can
then introduce maps for each kind of hash tables to further distinguish.

R=mstarzinger@chromium.org

Bug: v8:6593
Change-Id: I1a532884758e571abdfe2e2743fc5ea611d12f7e
Reviewed-on: https://chromium-review.googlesource.com/581009
Commit-Queue: Yang Guo <yangguo@chromium.org>
Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#46828}