Add Element.nameLength getter and specialize it for LibraryElement.

pkg/analyzer/lib/src/generated/testing/element_factory.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.testing.element_factory;
 
 import 'dart:collection';
 
 import 'package:analyzer/src/generated/ast.dart';
 import 'package:analyzer/src/generated/constant.dart';
@@ skipping 424 matching lines @@
     spec.prefix = prefix;
     spec.combinators = combinators;
     return spec;
   }
 
   static LibraryElementImpl library(
       AnalysisContext context, String libraryName) {
     String fileName = "/$libraryName.dart";
     CompilationUnitElementImpl unit = compilationUnit(fileName);
     LibraryElementImpl library =
-        new LibraryElementImpl(context, libraryName, 0);
+        new LibraryElementImpl(context, libraryName, 0, libraryName.length);
     library.definingCompilationUnit = unit;
     return library;
   }
 
   static LocalVariableElementImpl localVariableElement(Identifier name) =>
       new LocalVariableElementImpl.forNode(name);
 
   static LocalVariableElementImpl localVariableElement2(String name) =>
       new LocalVariableElementImpl(name, 0);
 
@@ skipping 148 matching lines @@
     }
     return variable;
   }
 
   static TypeParameterElementImpl typeParameterElement(String name) {
     TypeParameterElementImpl element = new TypeParameterElementImpl(name, 0);
     element.type = new TypeParameterTypeImpl(element);
     return element;
   }
 }