Mark the ET_MOUSE_MOVED created from a pointer grab as synthesized.

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 69 matching lines @@
   }
   return nullptr;
 }
 
 // Translates a XEvent into a ui::Event.
 std::unique_ptr<ui::Event> TranslateXEventToEvent(const XEvent& xev) {
   int flags = EventFlagsFromXEvent(xev);
   switch (xev.type) {
     case LeaveNotify:
     case EnterNotify:
-      // EnterNotify creates ET_MOUSE_MOVED. Mark as synthesized as this is
-      // not real mouse move event.
-      if (xev.type == EnterNotify)
-        flags |= EF_IS_SYNTHESIZED;
       return base::MakeUnique<MouseEvent>(ET_MOUSE_MOVED,
                                           EventLocationFromXEvent(xev),
                                           EventSystemLocationFromXEvent(xev),
                                           EventTimeFromXEvent(xev), flags, 0);
 
     case KeyPress:
     case KeyRelease:
       return base::MakeUnique<KeyEvent>(EventTypeFromXEvent(xev),
                                         KeyboardCodeFromXKeyEvent(&xev), flags);
 
@@ skipping 93 matching lines @@
 
 void X11EventSourceLibevent::OnFileCanReadWithoutBlocking(int fd) {
   event_source_.DispatchXEvents();
 }
 
 void X11EventSourceLibevent::OnFileCanWriteWithoutBlocking(int fd) {
   NOTREACHED();
 }
 
 }  // namespace ui