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

pkg/front_end/lib/src/fasta/kernel/kernel_class_builder.dart

Index: pkg/front_end/lib/src/fasta/kernel/kernel_class_builder.dart
diff --git a/pkg/front_end/lib/src/fasta/kernel/kernel_class_builder.dart b/pkg/front_end/lib/src/fasta/kernel/kernel_class_builder.dart
index 8240de74216fe90478169078fb7bb248809eb087..45ca2c205e5216975af31f2621c3c689feaf18cb 100644
--- a/pkg/front_end/lib/src/fasta/kernel/kernel_class_builder.dart
+++ b/pkg/front_end/lib/src/fasta/kernel/kernel_class_builder.dart
@@ -39,9 +39,9 @@ abstract class KernelClassBuilder
       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;