Remove deprecated_warning.

pkg/front_end/lib/src/fasta/messages.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.messages;
 
 import 'dart:io' show exitCode;
 
 import 'package:kernel/ast.dart' show Library, Location, Program, TreeNode;
 
@@ skipping 40 matching lines @@
   if (hideNits) return;
   print(
       deprecated_format(uri, charOffset, colorNit("Nit: ${message.message}")));
   if (nitsAreFatal) {
     if (isVerbose) print(StackTrace.current);
     throw new deprecated_InputError(
         uri, charOffset, "Compilation aborted due to fatal nits.");
   }
 }
 
-void deprecated_warning(Uri uri, int charOffset, String message) {
-  if (hideWarnings) return;
-  print(deprecated_format(uri, charOffset, colorWarning("Warning: $message")));
-  if (warningsAreFatal) {
-    if (isVerbose) print(StackTrace.current);
-    throw new deprecated_InputError(
-        uri, charOffset, "Compilation aborted due to fatal warnings.");
-  }
-}
-
 String colorWarning(String message) {
   // TODO(ahe): Colors need to be optional. Doesn't work well in Emacs or on
   // Windows.
   return magenta(message);
 }
 
 String colorNit(String message) {
   // TODO(ahe): Colors need to be optional. Doesn't work well in Emacs or on
   // Windows.
   return cyan(message);
@@ skipping 52 matching lines @@
       program.libraries.clear();
       parent.parent = null;
       return result;
     } else {
       return null;
     }
   } else {
     return node.location;
   }
 }