Fix gn build.

TBR=ishell@chromium.org

Review URL: https://codereview.chromium.org/723463002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@25277 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Fix windows build (static_cast missing).

TBR=ishell@chromium.org

Review URL: https://codereview.chromium.org/714413005

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@25278 ce2b1a6d-e550-0410-aec6-3dcde31c8c00