Revert "Remove 'Element.docRange'."

pkg/analyzer/lib/src/summary/summarize_elements.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.
 
 library serialization.elements;
 
 import 'dart:convert';
 
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/element/element.dart';
@@ skipping 703 matching lines @@
    * Serialize documentation from the given [element], creating an
    * [UnlinkedDocumentationComment].
    *
    * If [element] has no documentation, `null` is returned.
    */
   UnlinkedDocumentationCommentBuilder serializeDocumentation(Element element) {
     if (element.documentationComment == null) {
       return null;
     }
     return new UnlinkedDocumentationCommentBuilder(
-        text: element.documentationComment);
+        text: element.documentationComment,
+        offset: element.docRange.offset,
+        length: element.docRange.length);
   }
 
   /**
    * Serialize the given [enumElement], creating an [UnlinkedEnum].
    */
   UnlinkedEnumBuilder serializeEnum(ClassElement enumElement) {
     UnlinkedEnumBuilder b = new UnlinkedEnumBuilder();
     b.name = enumElement.name;
     b.nameOffset = enumElement.nameOffset;
     List<UnlinkedEnumValueBuilder> values = <UnlinkedEnumValueBuilder>[];
@@ skipping 975 matching lines @@
       exportNames.add(new LinkedExportNameBuilder(
           name: name,
           dependency: serializeDependency(dependentLibrary),
           unit: unit,
           kind: kind));
     }
     pb.exportNames = exportNames;
     return pb;
   }
 }