Allow initializing a field in a superclass in a const constructor.

compiler/java/com/google/dart/compiler/resolver/Elements.java

 // Copyright (c) 2011, 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.
 
 package com.google.dart.compiler.resolver;
 
 import com.google.common.annotations.VisibleForTesting;
 import com.google.dart.compiler.ast.DartClass;
 import com.google.dart.compiler.ast.DartField;
 import com.google.dart.compiler.ast.DartFunctionExpression;
@@ skipping 165 matching lines @@
   }
 
   public static MethodElement lookupLocalMethod(ClassElement cls, String name) {
     return ((ClassElementImplementation) cls).lookupLocalMethod(name);
   }
 
   public static FieldElement lookupLocalField(ClassElement cls, String name) {
     return ((ClassElementImplementation) cls).lookupLocalField(name);
   }
 
+  public static FieldElement lookupField(ClassElement cls, String name) {
+    return ((ClassElementImplementation) cls).lookupField(name);
+  }
+
   static ConstructorElement constructorNamed(String name, ClassElement declaringClass,
                                              ClassElement constructorType) {
     return ConstructorElementImplementation.named(name, declaringClass, constructorType);
   }
 
   public static FunctionAliasElement functionTypeAliasFromNode(DartFunctionTypeAlias node,
                                                                LibraryElement library) {
     return FunctionAliasElementImplementation.fromNode(node, library);
   }
 
@@ skipping 24 matching lines @@
     return VoidElement.getInstance();
   }
 
   /**
    * Returns true if the class needs an implicit default constructor.
    */
   public static boolean needsImplicitDefaultConstructor(ClassElement classElement) {
     return !classElement.isObject() && classElement.getConstructors().isEmpty();
   }
 }