Corrects the regression of [a-z] keys for non-US layouts would have wrong VKEY code if CAPSLOCK is …

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/keysym.h>
@@ skipping 458 matching lines @@
   // 5. If not found, fallback to find keysym + keysym_shift + hardware_code
   //    in map2.
   // 6. If not found, fallback to find keysym + keysym_shift + keysym_altgr +
   //    hardware_code in map3.
   // 7. If not found, fallback to find in KeyboardCodeFromXKeysym(), which
   //    mainly for non-letter keys.
   // 8. If not found, fallback to find with the hardware code in US layout.
 
   KeySym keysym = NoSymbol;
   XKeyEvent xkey = xev->xkey;
-  xkey.state &= ~(ShiftMask | Mod1Mask);
+  xkey.state &= (~0xFF | Mod2Mask);  // Clears the xkey's state except numlock.
   // XLookupKeysym does not take into consideration the state of the lock/shift
   // etc. keys. So it is necessary to use XLookupString instead.
   XLookupString(&xkey, NULL, 0, &keysym, NULL);
 
   // [a-z] cases.
   if (keysym >= XK_a && keysym <= XK_z)
     return static_cast<KeyboardCode>(VKEY_A + keysym - XK_a);
 
   // [0-9] cases.
   if (keysym >= XK_0 && keysym <= XK_9)
@@ skipping 780 matching lines @@
     case VKEY_KBD_BRIGHTNESS_UP:
       return XF86XK_KbdBrightnessUp;
 
     default:
       LOG(WARNING) << "Unknown keycode:" << keycode;
       return 0;
     }
 }
 
 }  // namespace ui