Parser: add usage counters for "use asm".

R=jochen@chromium.org
BUG=

Review URL: https://codereview.chromium.org/336863007

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@22093 ce2b1a6d-e550-0410-aec6-3dcde31c8c00