Fix warnings about unimplemented methods in serialized element model.

pkg/compiler/lib/src/serialization/modelz.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.
 
 /// Implementation of the element model used for deserialiation.
 ///
 /// These classes are created by [ElementDeserializer] triggered by the
 /// [Deserializer].
 
 library dart2js.serialization.modelz;
@@ skipping 73 matching lines @@
 
   @override
   ClassElement get enclosingClass => null;
 
   @override
   Element get enclosingClassOrCompilationUnit {
     return _unsupported('enclosingClassOrCompilationUnit');
   }
 
   @override
-  String get fixedBackendName => _unsupported('fixedBackendName');
-
-  @override
   LibraryElement get implementationLibrary => library;
 
   @override
   bool get isAbstract => false;
 
   @override
   bool get isAssignable => _unsupported('isAssignable');
 
   @override
   bool get isClassMember => false;
@@ skipping 861 matching lines @@
     return _unsupported('redirectionDeferredPrefix');
   }
 }
 
 class GenerativeConstructorElementZ extends ConstructorElementZ {
   GenerativeConstructorElementZ(ObjectDecoder decoder)
       : super(decoder);
 
   @override
   ElementKind get kind => ElementKind.GENERATIVE_CONSTRUCTOR;
+
+  @override
+  bool get isEffectiveTargetMalformed =>
+      _unsupported('isEffectiveTargetMalformed');
 }
 
 class FactoryConstructorElementZ extends ConstructorElementZ {
 
   FactoryConstructorElementZ(ObjectDecoder decoder)
       : super(decoder);
 
   @override
   ElementKind get kind => ElementKind.FACTORY_CONSTRUCTOR;
+
+  @override
+  bool get isEffectiveTargetMalformed =>
+      _unsupported('isEffectiveTargetMalformed');
 }
 
 abstract class MemberElementMixin
     implements DeserializedElementZ, MemberElement {
 
   @override
   MemberElement get memberContext => this;
 
   @override
   Name get memberName => new Name(name, library);
@@ skipping 549 matching lines @@
   }
 
   @override
   ElementKind get kind => ElementKind.PREFIX;
 
   @override
   Element lookupLocalMember(String memberName) {
     return _unsupported('lookupLocalMember');
   }
 }