Mark the ET_MOUSE_MOVED created from a pointer grab as synthesized.

ui/platform_window/x11/x11_window.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/platform_window/x11/x11_window.h"
 
 #include <X11/extensions/XInput2.h>
 #include <X11/Xlib.h>
 #include <X11/Xutil.h>
 
@@ skipping 69 matching lines @@
 }
 
 bool X11Window::CanDispatchEvent(const PlatformEvent& xev) {
   return IsEventForXWindow(*xev);
 }
 
 uint32_t X11Window::DispatchEvent(const PlatformEvent& event) {
   XEvent* xev = event;
   switch (xev->type) {
     case EnterNotify: {
-      // EnterNotify creates ET_MOUSE_MOVED. Mark as synthesized as this is
-      // not real mouse move event.
       MouseEvent mouse_event(xev);
       CHECK_EQ(ET_MOUSE_MOVED, mouse_event.type());
-      mouse_event.set_flags(mouse_event.flags() | EF_IS_SYNTHESIZED);
       delegate()->DispatchEvent(&mouse_event);
       break;
     }
     case LeaveNotify: {
       MouseEvent mouse_event(xev);
       delegate()->DispatchEvent(&mouse_event);
       break;
     }
 
     case KeyPress:
@@ skipping 37 matching lines @@
 
     case GenericEvent: {
       ProcessXInput2Event(xev);
       break;
     }
   }
   return POST_DISPATCH_STOP_PROPAGATION;
 }
 
 }  // namespace ui