Add documentationComment for Class to Kernel. Parse it. Resynthesize in Analyzer.

pkg/front_end/lib/src/fasta/source/source_library_builder.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.source_library_builder;
 
 import 'package:kernel/ast.dart' show ProcedureKind;
 
 import '../../base/resolve_relative_uri.dart' show resolveRelativeUri;
 
@@ skipping 179 matching lines @@
     parts.add(loader.read(resolvedUri, charOffset,
         fileUri: newFileUri, accessor: this));
   }
 
   void addPartOf(List<MetadataBuilder> metadata, String name, String uri) {
     partOfName = name;
     partOfUri = uri;
   }
 
   void addClass(
+      String documentationComment,
       List<MetadataBuilder> metadata,
       int modifiers,
       String name,
       List<TypeVariableBuilder> typeVariables,
       T supertype,
       List<T> interfaces,
       int charOffset);
 
   void addNamedMixinApplication(
       List<MetadataBuilder> metadata,
@@ skipping 435 matching lines @@
   /// synthesize type variables on the factory matching the class'.
   void addFactoryDeclaration(
       ProcedureBuilder procedure, DeclarationBuilder<T> factoryDeclaration) {
     factoryDeclarations[procedure] = factoryDeclaration;
   }
 
   Scope toScope(Scope parent) {
     return new Scope(members, setters, parent, isModifiable: false);
   }
 }