Previously, removing an element in the middle made it consume space
forever. This fixes that, without changing the complexity of removal /
addition. The trade-off is that RemoveOne will shuffle indices (which should be
OK for the current users).
BUG=v8:7308
Change-Id: I0373e30f2d9d1ffb93a78d383d41b500dbbf3429
Reviewed-on: https://chromium-review.googlesource.com/1159371
Commit-Queue: Marja Hölttä <marja@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54875}