Dart == calls now are rewritten to an Identical node (if applicable),
which can then be specialized further into JS == and === nodes.
Previously, == calls would specialize directly to JS == and === nodes,
but some of these optimizations were then missed for the cases where
Identical nodes are introduced directly (e.g. for switch cases).
The rules have also changed a bit to be more effective, and there
are some small improvements to the utility functions.
BUG=
R=karlklose@google.com
Review URL: https://codereview.chromium.org//1276843008.
Asger Feldthaus
684b83ab05