Add toStructuredText to ConstantExpression and align method names with ConstantValue

pkg/compiler/lib/src/serialization/constant_serialization.dart

 // Copyright (c) 2015, 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 dart2js.serialization.constants;
 
 import '../constants/constructors.dart';
 import '../constants/expressions.dart';
 import '../dart_types.dart';
 import '../elements/elements.dart' show FieldElement;
@@ skipping 152 matching lines @@
 
   @override
   void visitStringLength(
       StringLengthConstantExpression exp, ObjectEncoder encoder) {
     encoder.setConstant(Key.EXPRESSION, exp.expression);
   }
 
   @override
   void visitDeferred(DeferredConstantExpression exp, ObjectEncoder encoder) {
     throw new UnsupportedError(
-        "ConstantSerializer.visitDeferred: ${exp.getText()}");
+        "ConstantSerializer.visitDeferred: ${exp.toDartText()}");
   }
 }
 
 /// Utility class for deserializing [ConstantExpression]s.
 ///
 /// This is used by the [Deserializer].
 class ConstantDeserializer {
   /// Deserializes a [ConstantExpression] from an [ObjectDecoder].
   ///
   /// The class is called from the [Deserializer] when a [ConstantExpression]
@@ skipping 206 matching lines @@
             readFields(), readConstructorInvocation());
       case ConstantConstructorKind.REDIRECTING_GENERATIVE:
         return new RedirectingGenerativeConstantConstructor(
             readDefaults(), readConstructorInvocation());
       case ConstantConstructorKind.REDIRECTING_FACTORY:
         return new RedirectingFactoryConstantConstructor(
             readConstructorInvocation());
     }
   }
 }