Fix some surprising reverse key mappings.

chrome/browser/chromeos/events/event_rewriter.cc

 // Copyright 2014 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 "chrome/browser/chromeos/events/event_rewriter.h"
 
 #include <vector>
 
 #include "ash/sticky_keys/sticky_keys_controller.h"
 #include "ash/wm/window_state.h"
@@ skipping 246 matching lines @@
   if (xev) {
     XEvent xkeyevent;
     // Convert all XI2-based key events into X11 core-based key events,
     // until consumers no longer depend on receiving X11 core events.
     if (xev->type == GenericEvent)
       ui::InitXKeyEventFromXIDeviceEvent(*xev, &xkeyevent);
     else
       xkeyevent.xkey = xev->xkey;
 
     // Update native event to match rewritten |ui::Event|.
-    xkeyevent.xkey.keycode = XKeysymToKeycode(
-        gfx::GetXDisplay(),
-        ui::XKeysymForWindowsKeyCode(key_code, flags & ui::EF_SHIFT_DOWN));
+    // The X11 keycode represents a physical key position, so it shouldn't
+    // change unless we have actually changed keys, not just modifiers.
+    // This is one guard against problems like crbug.com/390263.
+    if (key_event.key_code() != key_code) {
+      xkeyevent.xkey.keycode =
+          XKeyCodeForWindowsKeyCode(key_code, flags, gfx::GetXDisplay());
+    }
+
     UpdateX11EventMask(flags, &xkeyevent.xkey.state);
     ui::KeyEvent x11_key_event(&xkeyevent, false);
     rewritten_key_event = new ui::KeyEvent(x11_key_event);
   }
 #endif
   if (!rewritten_key_event)
     rewritten_key_event = new ui::KeyEvent(key_event);
   rewritten_key_event->set_flags(flags);
   rewritten_key_event->set_key_code(key_code);
   rewritten_key_event->set_character(
@@ skipping 657 matching lines @@
     KeyboardDeviceAddedInternal(device_info[i].deviceid, device_info[i].name);
   }
 
   XIFreeDeviceInfo(device_info);
 #else
   KeyboardDeviceAddedInternal(device_id, "keyboard");
 #endif
 }
 
 }  // namespace chromeos