Mark mouse events created for Enter/Leave notify as synthesized as they're not real mouse events.

ui/aura/root_window_host_x11.cc

 // Copyright (c) 2012 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/aura/root_window_host_x11.h"
 
 #include <strings.h>
 #include <X11/cursorfont.h>
 #include <X11/extensions/Xfixes.h>
 #include <X11/extensions/XInput2.h>
@@ skipping 440 matching lines @@
   XDestroyWindow(xdisplay_, xwindow_);
 }
 
 bool RootWindowHostX11::Dispatch(const base::NativeEvent& event) {
   XEvent* xev = event;
 
   if (FindEventTarget(event) == x_root_window_)
     return DispatchEventForRootWindow(event);
 
   switch (xev->type) {
-    case EnterNotify:
+    case EnterNotify: {
+      ui::MouseEvent mouse_event(xev);
+      // EnterNotify creates ET_MOUSE_MOVE. Mark as synthesized as this is not
+      // real mouse move event.
+      mouse_event.set_flags(mouse_event.flags() | ui::EF_IS_SYNTHESIZED);
+      TranslateAndDispatchMouseEvent(&mouse_event);
+      break;
+    }
     case LeaveNotify: {
       ui::MouseEvent mouse_event(xev);
       TranslateAndDispatchMouseEvent(&mouse_event);
       break;
     }
     case Expose: {
       gfx::Rect damage_rect(xev->xexpose.x, xev->xexpose.y,
                             xev->xexpose.width, xev->xexpose.height);
       delegate_->AsRootWindow()->ScheduleRedrawRect(damage_rect);
       break;
@@ skipping 667 matching lines @@
 }
 
 namespace test {
 
 void SetUseOverrideRedirectWindowByDefault(bool override_redirect) {
   default_override_redirect = override_redirect;
 }
 
 }  // namespace test
 }  // namespace aura