Sort the Dart vm flags before printing them out with the --print-flags option.

runtime/vm/flags.h

 // Copyright (c) 2012, 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.
 
 #ifndef VM_FLAGS_H_
 #define VM_FLAGS_H_
 
 #include "platform/assert.h"
 #include "vm/globals.h"
 
@@ skipping 55 matching lines @@
 
   static bool Initialized() { return initialized_; }
 
  private:
   static Flag* flags_;
 
   static bool initialized_;
 
   static void Parse(const char* option);
 
+  static int CompareFlagNames(const void* left, const void* right);
+
+  static void PrintFlags();
+
   // Testing needs direct access to private methods.
   friend void Dart_TestParseFlags();
 
   DISALLOW_ALLOCATION();
   DISALLOW_IMPLICIT_CONSTRUCTORS(Flags);
 };
 
 }  // namespace dart
 
 #endif  // VM_FLAGS_H_