Put back the code that I accidentally removed in crrev.com/17099003

ui/aura/root_window_host_x11.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/aura/root_window_host_x11.h"
 
 #include <strings.h>
 #include <X11/cursorfont.h>
 #include <X11/extensions/Xfixes.h>
 #include <X11/extensions/XInput2.h>
@@ skipping 395 matching lines @@
   // Likewise, the X server needs to know this window's pid so it knows which
   // program to kill if the window hangs.
   pid_t pid = getpid();
   XChangeProperty(xdisplay_,
                   xwindow_,
                   atom_cache_.GetAtom("_NET_WM_PID"),
                   XA_CARDINAL,
                   32,
                   PropModeReplace,
                   reinterpret_cast<unsigned char*>(&pid), 1);
+
+  XRRSelectInput(xdisplay_, x_root_window_,
+                 RRScreenChangeNotifyMask | RROutputChangeNotifyMask);
   Env::GetInstance()->AddObserver(this);
 }
 
 RootWindowHostX11::~RootWindowHostX11() {
   Env::GetInstance()->RemoveObserver(this);
   base::MessagePumpAuraX11::Current()->RemoveDispatcherForRootWindow(this);
   base::MessagePumpAuraX11::Current()->RemoveDispatcherForWindow(xwindow_);
 
   UnConfineCursor();
 
@@ skipping 671 matching lines @@
 }
 
 namespace test {
 
 void SetUseOverrideRedirectWindowByDefault(bool override_redirect) {
   default_override_redirect = override_redirect;
 }
 
 }  // namespace test
 }  // namespace aura