Fix some surprising reverse key mappings.

ui/events/keycodes/keyboard_code_conversion_x.cc

 // 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.
 
 #include "ui/events/keycodes/keyboard_code_conversion_x.h"
 
 #include <algorithm>
 
 #define XK_3270  // for XK_3270_BackTab
 #include <X11/XF86keysym.h>
@@ skipping 1309 matching lines @@
   xkeyevent->xkey.time = xievent->time;
   xkeyevent->xkey.x = xievent->event_x;
   xkeyevent->xkey.y = xievent->event_y;
   xkeyevent->xkey.x_root = xievent->root_x;
   xkeyevent->xkey.y_root = xievent->root_y;
   xkeyevent->xkey.state = xievent->mods.effective;
   xkeyevent->xkey.keycode = xievent->detail;
   xkeyevent->xkey.same_screen = 1;
 }
 
+unsigned int XKeyCodeForWindowsKeyCode(ui::KeyboardCode key_code,
+                                       int flags,
+                                       XDisplay* display) {
+  // SHIFT state is ignored in the call to XKeysymForWindowsKeyCode() here
+  // because we map the XKeysym back to a keycode, i.e. a physical key position.
+  // Using a SHIFT-modified XKeysym would sometimes yield X keycodes that,
+  // while technically valid, may be surprising in that they do not match
+  // the keycode of the original press, and conflict with assumptions in
+  // other code.
+  //
+  // For example, in a US layout, Shift-9 has the interpretation XK_parenleft,
+  // but the keycode KEY_9 alone does not map to XK_parenleft; instead,
+  // XKeysymToKeycode() returns KEY_KPLEFTPAREN (keypad left parenthesis)
+  // which does map to XK_parenleft -- notwithstanding that keyboards with
+  // dedicated number pad parenthesis keys are currently uncommon.
+  //
+  // Similarly, Shift-Comma has the interpretation XK_less, but KEY_COMMA
+  // alone does not map to XK_less; XKeysymToKeycode() returns KEY_102ND
+  // (the '<>' key between Shift and Z on 105-key keyboards) which does.
+  //
+  // crbug.com/386066 and crbug.com/390263 are examples of problems
+  // associated with this.
+  //
+  return XKeysymToKeycode(display, XKeysymForWindowsKeyCode(key_code, false));
+}
+
 }  // namespace ui