Oilpan: Fix more uninitialized RawPtrs for the oilpan build.

TBR=haraken@chromium.org, zerny@chromium.org
NOTRY=true

Review URL: https://codereview.chromium.org/220233007

git-svn-id: svn://svn.chromium.org/blink/trunk@170569 bbb929c8-8fbe-4397-9dbb-9b2b20218538