Add Element.nameLength getter and specialize it for LibraryElement.

pkg/analyzer/lib/src/generated/element_handle.dart

 // Copyright (c) 2014, 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 engine.element_handle;
 
 import 'ast.dart';
 import 'element.dart';
 import 'engine.dart';
 import 'java_core.dart';
@@ skipping 353 matching lines @@
   @override
   ElementLocation get location => _location;
 
   @override
   List<ElementAnnotation> get metadata => actualElement.metadata;
 
   @override
   String get name => actualElement.name;
 
   @override
+  int get nameLength => actualElement.nameLength;
+
+  @override
   int get nameOffset => actualElement.nameOffset;
 
   @deprecated
   @override
   AstNode get node => computeNode();
 
   @override
   Source get source => actualElement.source;
 
   @override
@@ skipping 729 matching lines @@
 }
 
 /**
  * TODO(scheglov) invalid implementation
  */
 class WeakReference<T> {
   final T value;
   WeakReference(this.value);
   T get() => value;
 }