This unifies phases in SimplifiedLowering, and will enable
more optimizations, i.e. we can do the output representation
during typing then, which in turn should allow us to use the
feedback type even in unchecked operators (i.e. NumberAbs).

R=jarin@chromium.org

Review-Url: https://codereview.chromium.org/2137003002
Cr-Commit-Position: refs/heads/master@{#37639}