Regularly poll the X11 event queue.

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.h"
 
 #include <X11/Xlib.h>
 
 #include "base/message_loop/message_loop.h"
 #include "base/message_loop/message_pump_libevent.h"
 
 namespace ui {
 
 namespace {
 
 class X11EventSourceLibevent : public X11EventSource,
+                               public base::MessagePumpLibevent::EventSource,
                                public base::MessagePumpLibevent::Watcher {
  public:
   explicit X11EventSourceLibevent(XDisplay* display)
       : X11EventSource(display),
         initialized_(false) {
     AddEventWatcher();
   }
 
   ~X11EventSourceLibevent() override {
+    if (initialized_)
+      base::MessageLoopForUI::current()->ClearEventSource();
   }
 
  private:
   void AddEventWatcher() {
     if (initialized_)
       return;
     if (!base::MessageLoop::current())
       return;
 
     int fd = ConnectionNumber(display());
-    base::MessageLoopForUI::current()->WatchFileDescriptor(fd, true,
-        base::MessagePumpLibevent::WATCH_READ, &watcher_controller_, this);
+    base::MessageLoopForUI::current()->WatchFileDescriptor(
+        fd, true, base::MessagePumpLibevent::WATCH_READ, &watcher_controller_,
+        this);
+    base::MessageLoopForUI::current()->SetEventSource(this);
     initialized_ = true;
   }
 
   // PlatformEventSource:
-  void OnDispatcherListChanged() override {
-    AddEventWatcher();
-  }
+  void OnDispatcherListChanged() override { AddEventWatcher(); }
+
+  // base::MessagePumpLibEvent::EventSource:
+  bool Poll() override { return DispatchXEvents(); }
 
   // base::MessagePumpLibevent::Watcher:
   void OnFileCanReadWithoutBlocking(int fd) override {
     DispatchXEvents();
   }
 
   void OnFileCanWriteWithoutBlocking(int fd) override {
     NOTREACHED();
   }
 
   base::MessagePumpLibevent::FileDescriptorWatcher watcher_controller_;
   bool initialized_;
 
   DISALLOW_COPY_AND_ASSIGN(X11EventSourceLibevent);
 };
 
 }  // namespace
 
 scoped_ptr<PlatformEventSource> PlatformEventSource::CreateDefault() {
   return make_scoped_ptr(new X11EventSourceLibevent(gfx::GetXDisplay()));
 }
 
 }  // namespace ui