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

pkg/front_end/lib/src/fasta/source/outline_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.outline_builder;
 
 import 'package:kernel/ast.dart' show ProcedureKind;
 
 import '../../scanner/token.dart' show Token;
 
@@ skipping 265 matching lines @@
 
   @override
   void endClassDeclaration(
       int interfacesCount,
       Token beginToken,
       Token classKeyword,
       Token extendsKeyword,
       Token implementsKeyword,
       Token endToken) {
     debugEvent("endClassDeclaration");
+
+    String documentationComment = null;
+    if (beginToken.precedingComments != null) {
+      documentationComment = beginToken.precedingComments.lexeme;
+      // TODO(scheglov): Add support for line comments.
+    }
+
     List<TypeBuilder> interfaces = popList(interfacesCount);
     TypeBuilder supertype = pop();
     List<TypeVariableBuilder> typeVariables = pop();
     int charOffset = pop();
     String name = pop();
     if (typeVariables != null && supertype is MixinApplicationBuilder) {
       supertype.typeVariables = typeVariables;
       supertype.subclassName = name;
     }
     int modifiers = Modifier.validate(pop());
     List<MetadataBuilder> metadata = pop();
-    library.addClass(metadata, modifiers, name, typeVariables, supertype,
-        interfaces, charOffset);
+    library.addClass(documentationComment, metadata, modifiers, name,
+        typeVariables, supertype, interfaces, charOffset);
     checkEmpty(beginToken.charOffset);
   }
 
   ProcedureKind computeProcedureKind(Token token) {
     if (token == null) return ProcedureKind.Method;
     if (optional("get", token)) return ProcedureKind.Getter;
     if (optional("set", token)) return ProcedureKind.Setter;
     return unhandled(
         token.lexeme, "computeProcedureKind", token.charOffset, uri);
   }
@@ skipping 577 matching lines @@
   Link<Token> handleMemberName(Link<Token> identifiers) {
     if (!enableNative || identifiers.isEmpty) return identifiers;
     return removeNativeClause(identifiers, stringExpectedAfterNative);
   }
 
   @override
   void debugEvent(String name) {
     // printEvent(name);
   }
 }