Handle exports of invalid types.

pkg/front_end/lib/src/fasta/builder/invalid_type_builder.dart

Index: pkg/front_end/lib/src/fasta/builder/invalid_type_builder.dart
diff --git a/pkg/front_end/lib/src/fasta/builder/invalid_type_builder.dart b/pkg/front_end/lib/src/fasta/builder/invalid_type_builder.dart
index 3135ad2e84fd456549b3ff881c2da42b2cd0c9e4..b17457099e819e456a4897f299015f8cccee32f0 100644
--- a/pkg/front_end/lib/src/fasta/builder/invalid_type_builder.dart
+++ b/pkg/front_end/lib/src/fasta/builder/invalid_type_builder.dart
@@ -4,10 +4,16 @@
 
 library fasta.invalid_type_builder;
 
-import 'builder.dart' show Builder, TypeBuilder, TypeDeclarationBuilder;
+import 'builder.dart'
+    show Builder, LibraryBuilder, TypeBuilder, TypeDeclarationBuilder;
 
 abstract class InvalidTypeBuilder<T extends TypeBuilder, R>
     extends TypeDeclarationBuilder<T, R> {
-  InvalidTypeBuilder(String name, Builder parent, int charOffset, [Uri fileUri])
-      : super(null, 0, name, parent, charOffset, fileUri);
+  InvalidTypeBuilder(String name, int charOffset, [Uri fileUri])
+      : super(null, 0, name, null, charOffset, fileUri);
+
+  Builder combineAmbiguousImport(
+      String name, Builder other, LibraryBuilder library) {
+    return this;
+  }
 }