Use UnaryOperator and BinaryOperator in ConstantSystem.

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

Index: pkg/compiler/lib/src/dart_backend/backend_ast_emitter.dart
diff --git a/pkg/compiler/lib/src/dart_backend/backend_ast_emitter.dart b/pkg/compiler/lib/src/dart_backend/backend_ast_emitter.dart
index bfda4ab0365cc5095c274206062271b87e4739c2..beb05de1da9dfeb3434ff3d9e21128967290515f 100644
--- a/pkg/compiler/lib/src/dart_backend/backend_ast_emitter.dart
+++ b/pkg/compiler/lib/src/dart_backend/backend_ast_emitter.dart
@@ -1259,6 +1259,12 @@ class ConstantEmitter
   }
 
   @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) {