This will allow the GC to differentiate between regular HashTables and EphemeronHashTables.

Bug: chromium:844008
Change-Id: I2f9009ac25eb117de03786b110dd362b829c5e9e
Reviewed-on: https://chromium-review.googlesource.com/1089066Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Dominik Inführ <dinfuehr@google.com>
Cr-Commit-Position: refs/heads/master@{#53577}