Revert r158912 due to tcmalloc corruption.

This also reverts r159311, which fixed a use-after-free introduced in
r158912.

BUG=305884,305080,301514
R=abarth@chromium.org, jochen@chromium.org

Review URL: https://codereview.chromium.org/26763003

git-svn-id: svn://svn.chromium.org/blink/trunk@159356 bbb929c8-8fbe-4397-9dbb-9b2b20218538