events: keycodes: Remove the stateless singleton instance of KeycodeConverter

ui/events/keycodes/keyboard_code_conversion_mac.mm

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #import "ui/events/keycodes/keyboard_code_conversion_mac.h"
 
 #include <algorithm>
 
 #import <Carbon/Carbon.h>
 
@@ skipping 527 matching lines @@
     characters = [event charactersIgnoringModifiers];
     if ([characters length] > 0)
       code = KeyboardCodeFromCharCode([characters characterAtIndex:0]);
     if (code)
       return code;
   }
   return KeyboardCodeFromKeyCode([event keyCode]);
 }
 
 const char* CodeFromNSEvent(NSEvent* event) {
-  return KeycodeConverter::GetInstance()->NativeKeycodeToCode(
-      [event keyCode]);
+  return ui::KeycodeConverter::NativeKeycodeToCode([event keyCode]);
 }
 
 }  // namespace ui