Fix warnings found by new closure compiler.

BUG=
R=aandrey@chromium.org, pfeldman@chromium.org

Review URL: https://codereview.chromium.org/78383002

git-svn-id: svn://svn.chromium.org/blink/trunk@162468 bbb929c8-8fbe-4397-9dbb-9b2b20218538