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

ui/events/keycodes/keyboard_code_conversion_x.h

Index: ui/events/keycodes/keyboard_code_conversion_x.h
diff --git a/ui/events/keycodes/keyboard_code_conversion_x.h b/ui/events/keycodes/keyboard_code_conversion_x.h
index 162669124db09331d99dc7b68dae7606b1462b37..3f6d5f06ded3bd5061f284ca1f23f5daf6372da6 100644
--- a/ui/events/keycodes/keyboard_code_conversion_x.h
+++ b/ui/events/keycodes/keyboard_code_conversion_x.h
@@ -35,10 +35,6 @@ 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);