Trying to reduce use of our self-baked data structures.

Bug: v8:7570
Change-Id: Ie4257911b388d320e4c5da5108cd763d3ab9299f
Reviewed-on: https://chromium-review.googlesource.com/1032555Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Commit-Queue: Peter Marshall <petermarshall@chromium.org>
Cr-Commit-Position: refs/heads/master@{#52840}