Oilpan: expand size of vector backing container when finalizing.
Oilpan: expand size of vector backing container when finalizing.

The finalization of vector buffers will currently finalize all slots
in the buffer, as the actually used subsequence cannot be determined by
the buffer. Hence, the buffer finalization needs to expand the size of
the container before iterating over the slots so as to avoid ASan
container overflow checks reporting false negatives.

R=haraken
BUG=475801

Review URL: https://codereview.chromium.org/1104803002

git-svn-id: bf5cd6ccde378db821296732a091cfbcf5285fbd@194360 bbb929c8-8fbe-4397-9dbb-9b2b20218538

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