Fix warnings in dart2js and analyzer caused by Fasta.

pkg/analyzer/lib/src/fasta/mock_element.dart

 // Copyright (c) 2016, 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 fasta.analyzer.mock_element;
 
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/dart/element/type.dart';
 
@@ skipping 40 matching lines @@
   bool get isSynthetic => internalError("not supported.");
 
   LibraryElement get library => internalError("not supported.");
 
   get location => internalError("not supported.");
 
   get metadata => internalError("not supported.");
 
   String get name => internalError("not supported.");
 
+  String get fullNameForErrors => name;
+
   int get nameLength => internalError("not supported.");
 
   int get nameOffset => -1;
 
   get unit => internalError("not supported.");
 
   accept<T>(visitor) => internalError("not supported.");
 
   String computeDocumentationComment() => internalError("not supported.");
 
@@ skipping 295 matching lines @@
   get constantValue => internalError("not supported.");
 
   computeConstantValue() => internalError("not supported.");
 
   void appendToWithoutDelimiters(StringBuffer buffer) {
     return internalError("not supported.");
   }
 
   FormalParameter computeNode() => internalError("not supported.");
 }