Use UnaryOperator and BinaryOperator in ConstantSystem.

pkg/compiler/lib/src/dart_backend/backend_ast_emitter.dart

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library backend_ast_emitter;
 
 import '../tree_ir/tree_ir_nodes.dart' as tree;
 import 'backend_ast_nodes.dart';
 import '../constants/expressions.dart';
 import '../constants/values.dart';
@@ skipping 1237 matching lines @@
                ..element = exp.element;
   }
 
   @override
   Expression visitBinary(BinaryConstantExpression exp,
                          BuilderContext<Statement> context) {
     return handlePrimitiveConstant(exp.value);
   }
 
   @override
+  Expression visitIdentical(IdenticalConstantExpression exp,
+                            BuilderContext<Statement> context) {
+    return handlePrimitiveConstant(exp.value);
+  }
+
+  @override
   Expression visitConditional(ConditionalConstantExpression exp,
                               BuilderContext<Statement> context) {
     if (exp.condition.value.isTrue) {
       return exp.trueExp.accept(this);
     } else {
       return exp.falseExp.accept(this);
     }
   }
 
   @override
@@ skipping 81 matching lines @@
       : super(name, ElementKind.VARIABLE, enclosingElement, variables, null);
 
   ExecutableElement get executableContext => enclosingElement;
 
   ExecutableElement get memberContext => executableContext.memberContext;
 
   bool get isLocal => true;
 
   LibraryElement get implementationLibrary => enclosingElement.library;
 }