This was pretty heavyweight.  It was kept in just for a few corner cases
that assumed it was there.  We can work around them by making sure that the
expression in a reified test context is always really the expression that
was visited in that context; and by inspecting the context manually and
consing up a pair of extra AST IDs for the unusual case of unary not in a
value AST context.

R=fschneider@chromium.org
BUG=
TEST=

Review URL: http://codereview.chromium.org/8386037

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@9863 ce2b1a6d-e550-0410-aec6-3dcde31c8c00