Robustified extension installation a bit.

Removed ADDRESS_SANITIZER #ifdefs, the extension is so tiny that it's
not worth the clutter.

R=dcarney@chromium.org

Review URL: https://codereview.chromium.org/138143014

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@18645 ce2b1a6d-e550-0410-aec6-3dcde31c8c00