linux: Do not fallback to the hardware keycodes for modifers.

ui/events/keycodes/keyboard_code_conversion_x.h

 // Copyright (c) 2011 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.
 
 #ifndef UI_EVENTS_KEYCODES_KEYBOARD_CODE_CONVERSION_X_H_
 #define UI_EVENTS_KEYCODES_KEYBOARD_CODE_CONVERSION_X_H_
 
 #include "base/basictypes.h"
 #include "ui/events/events_base_export.h"
 #include "ui/events/keycodes/keyboard_codes_posix.h"
@@ skipping 17 matching lines @@
                                                 bool shift);
 
 // Returns a XKeyEvent keycode (scancode) for a KeyboardCode. Keyboard layouts
 // are usually not injective, so inverse mapping should be avoided when
 // practical. A round-trip keycode -> KeyboardCode -> keycode will not
 // necessarily return the original keycode.
 EVENTS_BASE_EXPORT unsigned int XKeyCodeForWindowsKeyCode(KeyboardCode key_code,
                                                           int flags,
                                                           XDisplay* display);
 
-// Converts an X keycode into ui::KeyboardCode.
-EVENTS_BASE_EXPORT KeyboardCode
-    DefaultKeyboardCodeFromHardwareKeycode(unsigned int hardware_code);
-
 // Initializes a core XKeyEvent from an XI2 key event.
 EVENTS_BASE_EXPORT void InitXKeyEventFromXIDeviceEvent(const XEvent& src,
                                                        XEvent* dst);
 
 }  // namespace ui
 
 #endif  // UI_EVENTS_KEYCODES_KEYBOARD_CODE_CONVERSION_X_H_