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

pkg/front_end/lib/src/fasta/source/source_class_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_class_builder;
 
 import 'package:kernel/ast.dart'
     show Class, Constructor, Supertype, TreeNode, setParents;
 
 import '../dill/dill_member_builder.dart' show DillMemberBuilder;
@@ skipping 31 matching lines @@
   cls ??= new Class(name: name);
   cls.fileUri ??= parent.library.fileUri;
   if (cls.fileOffset == TreeNode.noOffset) {
     cls.fileOffset = charOffset;
   }
   return cls;
 }
 
 class SourceClassBuilder extends KernelClassBuilder {
   final Class cls;
+  final String documentationComment;
 
   final List<ConstructorReferenceBuilder> constructorReferences;
 
   KernelTypeBuilder mixedInType;
 
   SourceClassBuilder(
+      this.documentationComment,
       List<MetadataBuilder> metadata,
       int modifiers,
       String name,
       List<TypeVariableBuilder> typeVariables,
       KernelTypeBuilder supertype,
       List<KernelTypeBuilder> interfaces,
       Scope scope,
       Scope constructors,
       LibraryBuilder parent,
       this.constructorReferences,
@@ skipping 11 matching lines @@
       for (KernelTypeVariableBuilder t in typeVariables) {
         cls.typeParameters.add(t.parameter);
       }
       setParents(cls.typeParameters, cls);
       count += cls.typeParameters.length;
     }
     return count + super.resolveTypes(library);
   }
 
   Class build(KernelLibraryBuilder library, LibraryBuilder coreLibrary) {
+    cls.documentationComment = documentationComment;
+
     void buildBuilders(String name, Builder builder) {
       do {
         if (builder is KernelFieldBuilder) {
           // TODO(ahe): It would be nice to have a common interface for the
           // build method to avoid duplicating these two cases.
           cls.addMember(builder.build(library));
         } else if (builder is KernelFunctionBuilder) {
           cls.addMember(builder.build(library));
         } else {
           unhandled("${builder.runtimeType}", "buildBuilders",
@@ skipping 65 matching lines @@
   }
 
   @override
   void prepareInitializerInference(
       SourceLibraryBuilder library, ClassBuilder currentClass) {
     scope.forEach((name, builder) {
       builder.prepareInitializerInference(library, this);
     });
   }
 }