This CL changes some parts of the code to explicitly pass around a
Zone.  Not passing in a zone is okay too (in fact most of v8 still
doesn't), but that may incur a TLS lookup.

BUG=
TEST=

Review URL: https://chromiumcodereview.appspot.com/10443114

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@11709 ce2b1a6d-e550-0410-aec6-3dcde31c8c00