Fix a few nits found by PVS Studio

BUG=v8:3192
LOG=n
R=dslomov@chromium.org

Review URL: https://codereview.chromium.org/185563004

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@25086 ce2b1a6d-e550-0410-aec6-3dcde31c8c00