We don't need to pass |creationContext| to v8SetReturnValue family

Just a clean up. No change in behavior.

Review URL: https://codereview.chromium.org/50073004

git-svn-id: svn://svn.chromium.org/blink/trunk@160892 bbb929c8-8fbe-4397-9dbb-9b2b20218538