Fix some surprising reverse key mappings.

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"
 
 typedef union _XEvent XEvent;
+typedef struct _XDisplay XDisplay;
 
 namespace ui {
 
 EVENTS_BASE_EXPORT KeyboardCode KeyboardCodeFromXKeyEvent(const XEvent* xev);
 
 EVENTS_BASE_EXPORT KeyboardCode KeyboardCodeFromXKeysym(unsigned int keysym);
 
 EVENTS_BASE_EXPORT const char* CodeFromXEvent(const XEvent* xev);
 
 // Returns a character on a standard US PC keyboard from an XEvent.
 EVENTS_BASE_EXPORT uint16 GetCharacterFromXEvent(const XEvent* xev);
 
 // Converts a KeyboardCode into an X KeySym.
 EVENTS_BASE_EXPORT int XKeysymForWindowsKeyCode(KeyboardCode keycode,
                                                 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_