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

pkg/front_end/lib/src/fasta/dill/dill_member_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.dill_member_builder;
 
 import 'package:kernel/ast.dart' show
     Constructor,
     Field,
     Member,
@@ skipping 12 matching lines @@
     constMask,
     externalMask,
     finalMask,
     staticMask;
 
 class DillMemberBuilder extends MemberBuilder {
   final int modifiers;
 
   final Member member;
 
-  final Builder parent;
-
-  DillMemberBuilder(Member member, this.parent)
+  DillMemberBuilder(Member member, Builder parent)
       : modifiers = computeModifiers(member),
-        member = member;
+        member = member,
+        super(parent, member.fileOffset);
 
   Member get target => member;
 
   bool get isConstructor => member is Constructor;
 
   bool get isFactory {
     if (member is Procedure) {
       Procedure procedure = member;
       return procedure.kind == ProcedureKind.Factory;
     } else {
@@ skipping 12 matching lines @@
   } else if (member is Procedure) {
     modifier |= member.isConst ? constMask : 0;
     modifier |= member.isStatic ? staticMask : 0;
   } else if (member is Constructor) {
     modifier |= member.isConst ? constMask : 0;
   } else {
     internalError("Unhandled: ${member.runtimeType}");
   }
   return modifier;
 }