dart2js cps: Introduce some built-in operators in type propagation.

pkg/compiler/lib/src/tree_ir/tree_ir_tracer.dart

Index: pkg/compiler/lib/src/tree_ir/tree_ir_tracer.dart
diff --git a/pkg/compiler/lib/src/tree_ir/tree_ir_tracer.dart b/pkg/compiler/lib/src/tree_ir/tree_ir_tracer.dart
index cb1659b7688752adac610386e3bb7b72f693026b..fee1dd7adcb33d52b63659533e63a44f2bcabc96 100644
--- a/pkg/compiler/lib/src/tree_ir/tree_ir_tracer.dart
+++ b/pkg/compiler/lib/src/tree_ir/tree_ir_tracer.dart
@@ -509,6 +509,12 @@ class SubexpressionVisitor extends ExpressionVisitor<String> {
     String args = node.arguments.map(visitExpression).join(', ');
     return 'CreateInvocationMirror(${node.selector.name}, $args)';
   }
+
+  @override
+  String visitApplyBuiltinOperator(ApplyBuiltinOperator node) {
+    String args = node.arguments.map(visitExpression).join(', ');
+    return 'ApplyBuiltinOperator ${node.operator} ($args)';
+  }
 }
 
 /**