Use JavaScript runtime semantics when constant folding.

lib/compiler/implementation/leg.dart

Index: lib/compiler/implementation/leg.dart
diff --git a/lib/compiler/implementation/leg.dart b/lib/compiler/implementation/leg.dart
index 9e03df006f0934a20a27c60fe7a13106eacccced..efae2c4c751ff9db3ec201ba3fbd2b07c53cf029 100644
--- a/lib/compiler/implementation/leg.dart
+++ b/lib/compiler/implementation/leg.dart
@@ -27,10 +27,11 @@
 #source('code_buffer.dart');
 #source('compile_time_constants.dart');
 #source('compiler.dart');
+#source('constant_system_dart.dart');
+#source('constant_system_javascript.dart');
 #source('diagnostic_listener.dart');
 #source('enqueue.dart');
 #source('namer.dart');
-#source('operations.dart');
 #source('resolved_visitor.dart');
 #source('resolver.dart');
 #source('script.dart');