Remove deprecated_internalProblem.

pkg/front_end/lib/src/fasta/dill/dill_library_builder.dart

Index: pkg/front_end/lib/src/fasta/dill/dill_library_builder.dart
diff --git a/pkg/front_end/lib/src/fasta/dill/dill_library_builder.dart b/pkg/front_end/lib/src/fasta/dill/dill_library_builder.dart
index c25ec617f56aebf08e016444b77024bd306f0d89..315faf9dc15854a019abd62cd6f879236cf3b4e5 100644
--- a/pkg/front_end/lib/src/fasta/dill/dill_library_builder.dart
+++ b/pkg/front_end/lib/src/fasta/dill/dill_library_builder.dart
@@ -7,7 +7,7 @@ library fasta.dill_library_builder;
 import 'package:kernel/ast.dart'
     show Class, Field, Library, ListLiteral, Member, StaticGet, Typedef;
 
-import '../deprecated_problems.dart' show deprecated_internalProblem;
+import '../problems.dart' show unimplemented;
 
 import '../kernel/kernel_builder.dart'
     show
@@ -94,7 +94,7 @@ class DillLibraryBuilder extends LibraryBuilder<KernelTypeBuilder, Library> {
 
   @override
   void addToScope(String name, Builder member, int charOffset, bool isImport) {
-    deprecated_internalProblem("Not implemented yet.");
+    unimplemented("addToScope", charOffset, fileUri);
   }
 
   @override