Previously we assumed that control was always live after visiting an
expression, and that control was live to both basic block targets of an
expression in a test context.

Now we allow any expression to exit the graph.

R=fschneider@chromium.org,danno@chromium.org

Review URL: http://codereview.chromium.org/6839015

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@7601 ce2b1a6d-e550-0410-aec6-3dcde31c8c00