Oilpan: Roll back the allocation point if the allocation point is next to a promptly freed object.
Oilpan: Roll back the allocation point if the allocation point is next to a promptly freed object.

BUG=420515

Review URL: https://codereview.chromium.org/740253002

git-svn-id: bf5cd6ccde378db821296732a091cfbcf5285fbd@185754 bbb929c8-8fbe-4397-9dbb-9b2b20218538

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