OK, here's john's patch plus my sync stuff.

base/message_pump_aurax11.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 "base/message_pump_aurax11.h"
 
 #include <glib.h>
 #include <X11/X.h>
 #include <X11/extensions/XInput2.h>
 #include <X11/XKBlib.h>
@@ skipping 73 matching lines @@
 #endif
 
   return true;
 }
 
 Window FindEventTarget(const base::NativeEvent& xev) {
   Window target = xev->xany.window;
   if (xev->type == GenericEvent &&
       static_cast<XIEvent*>(xev->xcookie.data)->extension == g_xinput_opcode) {
     target = static_cast<XIDeviceEvent*>(xev->xcookie.data)->event;
+  } else if (xev->type == MapNotify) {
+    target = xev->xmap.window;
+  } else if (xev->type == UnmapNotify) {
+    target = xev->xunmap.window;
   }
+  // TODO(erg): Are there other events that we aren't reacting to properly
+  // because xev->xany.window != xev->eventname.window?
+
   return target;
 }
 
 bool InitializeXInput2() {
   static bool xinput2_supported = InitializeXInput2Internal();
   return xinput2_supported;
 }
 
 bool InitializeXkb() {
   Display* display = base::MessagePumpAuraX11::GetDefaultXDisplay();
@@ skipping 193 matching lines @@
   if (FindEventTarget(xev) == x_root_window_) {
     FOR_EACH_OBSERVER(MessagePumpDispatcher, root_window_dispatchers_,
                       Dispatch(xev));
     return true;
   }
   MessagePumpDispatcher* dispatcher = GetDispatcherForXEvent(xev);
   return dispatcher ? dispatcher->Dispatch(xev) : true;
 }
 
 }  // namespace base