Deprecate all diagnostics methods that use strings.

pkg/front_end/lib/src/fasta/dill/dill_library_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_library_builder;
 
 import 'package:kernel/ast.dart'
     show Class, Field, Library, ListLiteral, Member, StaticGet, Typedef;
 
-import '../errors.dart' show internalError;
+import '../deprecated_problems.dart' show deprecated_internalProblem;
 
 import '../kernel/kernel_builder.dart'
     show
         Builder,
         InvalidTypeBuilder,
         KernelInvalidTypeBuilder,
         KernelTypeBuilder,
         LibraryBuilder,
         Scope;
 
@@ skipping 66 matching lines @@
     return builder;
   }
 
   void addTypedef(Typedef typedef) {
     var typedefBuilder = new DillFunctionTypeAliasBuilder(typedef, this);
     addBuilder(typedef.name, typedefBuilder, typedef.fileOffset);
   }
 
   @override
   void addToScope(String name, Builder member, int charOffset, bool isImport) {
-    internalError("Not implemented yet.");
+    deprecated_internalProblem("Not implemented yet.");
   }
 
   @override
   Builder buildAmbiguousBuilder(
       String name, Builder builder, Builder other, int charOffset,
       {bool isExport: false, bool isImport: false}) {
     if (builder == other) return builder;
     if (builder is InvalidTypeBuilder) return builder;
     if (other is InvalidTypeBuilder) return other;
     // For each entry mapping key `k` to declaration `d` in `NS` an entry
     // mapping `k` to `d` is added to the exported namespace of `L` unless a
     // top-level declaration with the name `k` exists in `L`.
     if (builder.parent == this) return builder;
     return new KernelInvalidTypeBuilder(name, charOffset, fileUri);
   }
 
   @override
   String get fullNameForErrors {
     return library.name ?? "<library '${library.fileUri}'>";
   }
 }