Annotate native methods.

pkg/front_end/lib/src/fasta/builder/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.library_builder;
 
 import '../combinator.dart' show
     Combinator;
 
 import '../errors.dart' show
@@ skipping 54 matching lines @@
 
   bool addToExportScope(String name, Builder member);
 
   void addToScope(String name, Builder member);
 
   InvalidTypeBuilder buildAmbiguousBuilder(
       String name, Builder builder, Builder other, int charOffset);
 
   int finishStaticInvocations() => 0;
 
+  int finishNativeMethods() => 0;
+
   /// Looks up [constructorName] in the class named [className]. It's an error
   /// if no such class is exported by this library, or if the class doesn't
   /// have a matching constructor (or factory).
   ///
   /// If [constructorName] is null or the empty string, it's assumed to be an
   /// unnamed constructor.
   Builder getConstructor(String className,
       {String constructorName, bool isPrivate: false}) {
     constructorName ??= "";
     Builder cls = (isPrivate ? members : exports)[className];
@@ skipping 10 matching lines @@
       } else if (constructor.isFactory) {
         return constructor;
       }
     }
     throw internalError("Internal error: No constructor named"
         " '$className::$constructorName' in '$uri'.");
   }
 
   int finishTypeVariables(ClassBuilder object) => 0;
 }