Remove deprecated_addNit.

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

Index: pkg/front_end/lib/src/fasta/messages.dart
diff --git a/pkg/front_end/lib/src/fasta/messages.dart b/pkg/front_end/lib/src/fasta/messages.dart
index 5f3f7675370c1275bfff116bfe65e58df400d0d9..ae01d6f7f1f64cae62f7778dca11d58ea2e6f580 100644
--- a/pkg/front_end/lib/src/fasta/messages.dart
+++ b/pkg/front_end/lib/src/fasta/messages.dart
@@ -62,16 +62,6 @@ void deprecated_warning(Uri uri, int charOffset, String message) {
   }
 }
 
-void deprecated_nit(Uri uri, int charOffset, String message) {
-  if (hideNits) return;
-  print(deprecated_format(uri, charOffset, colorNit("Nit: $message")));
-  if (nitsAreFatal) {
-    if (isVerbose) print(StackTrace.current);
-    throw new deprecated_InputError(
-        uri, charOffset, "Compilation aborted due to fatal nits.");
-  }
-}
-
 String colorWarning(String message) {
   // TODO(ahe): Colors need to be optional. Doesn't work well in Emacs or on
   // Windows.