Move X11 device processing to worker threads

ui/events/platform/x11/x11_event_source.cc

Index: ui/events/platform/x11/x11_event_source.cc
diff --git a/ui/events/platform/x11/x11_event_source.cc b/ui/events/platform/x11/x11_event_source.cc
index 9268c425ca5ec6afc2fbbce33a4bd99c76ac33af..424b4be67a926ad58bd8bc716eeaf1a38ee9d5ca 100644
--- a/ui/events/platform/x11/x11_event_source.cc
+++ b/ui/events/platform/x11/x11_event_source.cc
@@ -86,13 +86,8 @@ X11EventSource::X11EventSource(XDisplay* display)
       continue_stream_(true) {
   CHECK(display_);
   DeviceDataManagerX11::CreateInstance();
-  hotplug_event_handler_.reset(
-      new X11HotplugEventHandler(DeviceDataManager::GetInstance()));
   InitializeXInput2(display_);
   InitializeXkb(display_);
-
-  // Force the initial device query to have an update list of active devices.
-  hotplug_event_handler_->OnHotplugEvent();
 }
 
 X11EventSource::~X11EventSource() {
@@ -155,4 +150,12 @@ void X11EventSource::StopCurrentEventStream() {
   continue_stream_ = false;
 }
 
+void X11EventSource::OnDispatcherListChanged() {
+  if (!hotplug_event_handler_) {
+    hotplug_event_handler_.reset(new X11HotplugEventHandler());
+    // Force the initial device query to have an update list of active devices.
+    hotplug_event_handler_->OnHotplugEvent();
+  }
+}
+
 }  // namespace ui