test-heap/TransitionsArraySimpleToFull was relying on an allocation
happening (and GC being triggered) right at the start of
TransitionsAccessor::Insert. That allocation would put the TransitionsAccessor
back to the kUninitialized state. If there's no allocation at that point of the
program logic, the test will fail, since the TransitionsAccessor will be go to
the kFullTransitionArray state.

(Needed for the in-place weak ref work, which will remove the allocation at that point.)

BUG=v8:7308

Change-Id: Id3985e107d86440fe05daf5f3f29c84d028df929
Reviewed-on: https://chromium-review.googlesource.com/995476Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Michael Stanton <mvstanton@chromium.org>
Commit-Queue: Marja Hölttä <marja@chromium.org>
Cr-Commit-Position: refs/heads/master@{#52374}