Remove deprecated_internalProblem.

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

Index: pkg/front_end/lib/src/fasta/builder/builder.dart
diff --git a/pkg/front_end/lib/src/fasta/builder/builder.dart b/pkg/front_end/lib/src/fasta/builder/builder.dart
index e3024e862040760b77e766e48fb170ad7cecbd37..91a1f7ae1e9807df0183ccaf6bbed72094b8fe45 100644
--- a/pkg/front_end/lib/src/fasta/builder/builder.dart
+++ b/pkg/front_end/lib/src/fasta/builder/builder.dart
@@ -4,7 +4,7 @@
 
 library fasta.builder;
 
-import '../deprecated_problems.dart' show deprecated_internalProblem;
+import '../problems.dart' show unhandled, unsupported;
 
 export 'class_builder.dart' show ClassBuilder;
 
@@ -44,7 +44,7 @@ export 'prefix_builder.dart' show PrefixBuilder;
 
 export 'invalid_type_builder.dart' show InvalidTypeBuilder;
 
-export '../scope.dart' show deprecated_AccessErrorBuilder, Scope, ScopeBuilder;
+export '../scope.dart' show AccessErrorBuilder, Scope, ScopeBuilder;
 
 export 'builtin_type_builder.dart' show BuiltinTypeBuilder;
 
@@ -124,8 +124,7 @@ abstract class Builder {
 
   bool get isSynthetic => false;
 
-  get target =>
-      deprecated_internalProblem("Unsupported operation $runtimeType.");
+  get target => unsupported("target", charOffset, fileUri);
 
   bool get hasProblem => false;
 
@@ -137,7 +136,7 @@ abstract class Builder {
       if (builder is LibraryBuilder) return builder.uri;
       builder = builder.parent;
     } while (builder != null);
-    return deprecated_internalProblem("No library parent.");
+    return unhandled("no library parent", "${runtimeType}", -1, null);
   }
 
   void prepareInitializerInference(