Use the location where FileDescriptorWatcher is created to track the libevent handlers

ui/events/platform/x11/x11_event_source_libevent.cc

 // Copyright 2014 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/events/platform/x11/x11_event_source_libevent.h"
 
 #include <X11/Xlib.h>
 #include <X11/extensions/XInput2.h>
 
 #include <memory>
@@ skipping 115 matching lines @@
 
     case GenericEvent:
       return TranslateXI2EventToEvent(xev);
   }
   return nullptr;
 }
 
 }  // namespace
 
 X11EventSourceLibevent::X11EventSourceLibevent(XDisplay* display)
-    : event_source_(this, display) {
+    : event_source_(this, display), watcher_controller_(FROM_HERE) {
   AddEventWatcher();
 }
 
 X11EventSourceLibevent::~X11EventSourceLibevent() {}
 
 // static
 X11EventSourceLibevent* X11EventSourceLibevent::GetInstance() {
   return static_cast<X11EventSourceLibevent*>(
       PlatformEventSource::GetInstance());
 }
@@ skipping 49 matching lines @@
 
 void X11EventSourceLibevent::OnFileCanReadWithoutBlocking(int fd) {
   event_source_.DispatchXEvents();
 }
 
 void X11EventSourceLibevent::OnFileCanWriteWithoutBlocking(int fd) {
   NOTREACHED();
 }
 
 }  // namespace ui