Ensure locations are always provided, but don't store them yet.

pkg/front_end/lib/src/fasta/kernel/kernel_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.kernel_class_builder;
 
 import 'package:kernel/ast.dart' show
     Class,
     DartType,
     ExpressionStatement,
@@ skipping 21 matching lines @@
 import 'redirecting_factory_body.dart' show
     RedirectingFactoryBody;
 
 abstract class KernelClassBuilder
     extends ClassBuilder<KernelTypeBuilder, InterfaceType> {
   KernelClassBuilder(
       List<MetadataBuilder> metadata, int modifiers,
       String name, List<TypeVariableBuilder> typeVariables,
       KernelTypeBuilder supertype, List<KernelTypeBuilder> interfaces,
       Map<String, Builder> members, List<KernelTypeBuilder> types,
-      LibraryBuilder parent)
+      LibraryBuilder parent, int charOffset)
       : super(metadata, modifiers, name, typeVariables, supertype, interfaces,
-          members, types, parent);
+          members, types, parent, charOffset);
 
   Class get cls;
 
   Class get target => cls;
 
   /// [arguments] have already been built.
   InterfaceType buildTypesWithBuiltArguments(List<DartType> arguments) {
     return arguments == null
         ? cls.rawType
         : new InterfaceType(cls,
@@ skipping 57 matching lines @@
               builder.body = new ExpressionStatement(
                   new Throw(new StringLiteral(message)));
             }
           }
         }
       });
     }
     return count;
   }
 }