[DomKey X11] Produce correct DomKey when Control is down

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 <stddef.h>
 
 #include <algorithm>
 
@@ skipping 886 matching lines @@
   } else {
     xkey = &xev->xkey;
   }
   KeySym keysym = XK_VoidSymbol;
   XLookupString(const_cast<XKeyEvent*>(xkey), NULL, 0, &keysym, NULL);
   return GetUnicodeCharacterFromXKeySym(keysym);
 }
 
 DomKey GetDomKeyFromXEvent(const XEvent* xev) {
   XEvent xkeyevent = {0};
-  const XKeyEvent* xkey = NULL;
+  XKeyEvent xkey;
   if (xev->type == GenericEvent) {
     // Convert the XI2 key event into a core key event so that we can
     // continue to use XLookupString() until crbug.com/367732 is complete.
     InitXKeyEventFromXIDeviceEvent(*xev, &xkeyevent);
-    xkey = &xkeyevent.xkey;
+    xkey = xkeyevent.xkey;
   } else {
-    xkey = &xev->xkey;
+    xkey = xev->xkey;
   }
+  // There is no good way to check whether a key combination will print a
+  // character on screen.
+  // e.g. On Linux US keyboard with French layout, |XLookupString()|
+  //        * Returns '?' for ctrl-shift-/
+  //        * Returns '§' for shift-/
+  //      According to spec the DomKey for ctrl-shift-/ should also be '§'.
+  // The solution is to take out ctrl modifier directly, as according to XKB map
+  // no keyboard combinations with ctrl key are mapped to printable character.
+  // https://crbug.com/633838
+  xkey.state &= ~ControlMask;
   KeySym keysym = XK_VoidSymbol;
-  XLookupString(const_cast<XKeyEvent*>(xkey), NULL, 0, &keysym, NULL);
+  XLookupString(&xkey, NULL, 0, &keysym, NULL);
   base::char16 ch = GetUnicodeCharacterFromXKeySym(keysym);
   return XKeySymToDomKey(keysym, ch);
 }
 
 KeyboardCode DefaultKeyboardCodeFromHardwareKeycode(
     unsigned int hardware_code) {
   // This function assumes that X11 is using evdev-based keycodes.
   static const KeyboardCode kHardwareKeycodeMap[] = {
       // Please refer to below links for the table content:
       // http://www.w3.org/TR/DOM-Level-3-Events-code/#keyboard-101
@@ skipping 476 matching lines @@
   // 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