Move modifier remapping code from X to Ash

ui/base/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/base/keycodes/keyboard_code_conversion_x.h"
 
 #define XK_3270  // for XK_3270_BackTab
 #include <X11/keysym.h>
 #include <X11/Xlib.h>
 #include <X11/Xutil.h>
@@ skipping 347 matching lines @@
       return VKEY_VOLUME_DOWN;
     case XF86XK_AudioRaiseVolume:
       return VKEY_VOLUME_UP;
     case XF86XK_MonBrightnessDown:
       return VKEY_BRIGHTNESS_DOWN;
     case XF86XK_MonBrightnessUp:
       return VKEY_BRIGHTNESS_UP;
 
     // TODO(sad): some keycodes are still missing.
   }
-  DLOG(WARNING) << "Unknown keysym: " << StringPrintf("0x%x", keysym);
+  if (keysym)
+    DLOG(WARNING) << "Unknown keysym: " << StringPrintf("0x%x", keysym);
   return VKEY_UNKNOWN;
 }
 
 uint16 GetCharacterFromXEvent(XEvent* xev) {
   char buf[6];
   int bytes_written = XLookupString(&xev->xkey, buf, 6, NULL, NULL);
   DCHECK_LE(bytes_written, 6);
 
   string16 result;
   return (bytes_written > 0 && UTF8ToUTF16(buf, bytes_written, &result) &&
@@ skipping 306 matching lines @@
     case VKEY_BRIGHTNESS_UP:
       return XF86XK_MonBrightnessUp;
 
     default:
       LOG(WARNING) << "Unknown keycode:" << keycode;
       return 0;
     }
 }
 
 }  // namespace ui