Add test coverage for DCE and type checks.

Rubber stamped by Geoffrey Garen.

* fast/js/dfg-cfg-simplify-eliminate-set-local-type-check-then-branch-not-null-and-decrement-expected.txt: Added.
* fast/js/dfg-cfg-simplify-eliminate-set-local-type-check-then-branch-not-null-and-decrement.html: Added.
* fast/js/dfg-cfg-simplify-eliminate-set-local-type-check-then-branch-not-null-expected.txt: Added.
* fast/js/dfg-cfg-simplify-eliminate-set-local-type-check-then-branch-not-null.html: Added.
* fast/js/jsc-test-list:
* fast/js/script-tests/dfg-cfg-simplify-eliminate-set-local-type-check-then-branch-not-null-and-decrement.js: Added.
(foo):
* fast/js/script-tests/dfg-cfg-simplify-eliminate-set-local-type-check-then-branch-not-null.js: Added.
(foo):



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@144879 268f45cc-cd09-0410-ab3c-d52691b4dbfc