aura-x11: Make sure the list of devices to track are updated when device hierarchy changes.

ui/aura/root_window_host_linux.cc

Index: ui/aura/root_window_host_linux.cc
diff --git a/ui/aura/root_window_host_linux.cc b/ui/aura/root_window_host_linux.cc
index a2c4a731a11e4153a0c838c901de236f53c38814..d577acd9425f00e116ef29e2a2fc8c01a9b810c0 100644
--- a/ui/aura/root_window_host_linux.cc
+++ b/ui/aura/root_window_host_linux.cc
@@ -344,10 +344,8 @@ RootWindowHostLinux::RootWindowHostLinux(const gfx::Rect& bounds)
   XFlush(xdisplay_);
 
   // TODO(sad): Re-enable once crbug.com/106516 is fixed.
-#if 0
   if (base::MessagePumpForUI::HasXInput2())
     ui::TouchFactory::GetInstance()->SetupXI2ForXWindow(xwindow_);
-#endif
 
   base::MessagePumpX::SetDefaultDispatcher(this);
   MessageLoopForUI::current()->AddDestructionObserver(this);
@@ -422,6 +420,13 @@ base::MessagePumpDispatcher::DispatchStatus RootWindowHostLinux::Dispatch(
       if (!factory->ShouldProcessXI2Event(xev))
         break;
 
+      // Update the device list if necessary.
+      if (xev->xgeneric.evtype == XI_HierarchyChanged) {
+        factory->UpdateDeviceList(xdisplay_);
+        handled = true;
+        break;
+      }
+
       // If this is a motion event we want to coalesce all pending motion
       // events that are at the top of the queue.
       XEvent last_event;