Mark the ET_MOUSE_MOVED created from a pointer grab as synthesized.

ui/aura/window_tree_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/window_tree_host_x11.h"
 
 #include <strings.h>
 #include <X11/cursorfont.h>
 #include <X11/extensions/XInput2.h>
 #include <X11/extensions/Xrandr.h>
@@ skipping 234 matching lines @@
         if (xev->type == EnterNotify) {
           aura::Window* root_window = window();
           client::CursorClient* cursor_client =
               client::GetCursorClient(root_window);
           if (cursor_client) {
             const display::Display display =
                 display::Screen::GetScreen()->GetDisplayNearestWindow(
                     root_window);
             cursor_client->SetDisplay(display);
           }
-          // EnterNotify creates ET_MOUSE_MOVE. Mark as synthesized as this is
-          // not a real mouse move event.
-          mouse_event.set_flags(mouse_event.flags() | ui::EF_IS_SYNTHESIZED);
         }
 
         TranslateAndDispatchLocatedEvent(&mouse_event);
         break;
       }
       case ui::ET_MOUSEWHEEL: {
         ui::MouseWheelEvent mouseev(xev);
         TranslateAndDispatchLocatedEvent(&mouseev);
         break;
       }
@@ skipping 285 matching lines @@
     ui::LocatedEvent* event) {
   SendEventToSink(event);
 }
 
 // static
 WindowTreeHost* WindowTreeHost::Create(const gfx::Rect& bounds_in_pixels) {
   return new WindowTreeHostX11(bounds_in_pixels);
 }
 
 }  // namespace aura