Cleanup v8 usage in modules

Followup to:
Cleanup v8 usage in core
https://codereview.chromium.org/318843003/

Review URL: https://codereview.chromium.org/319653002

git-svn-id: svn://svn.chromium.org/blink/trunk@175549 bbb929c8-8fbe-4397-9dbb-9b2b20218538