Mark the ET_MOUSE_MOVED created from a pointer grab as synthesized.

ui/aura/window_tree_host_x11.cc

Index: ui/aura/window_tree_host_x11.cc
diff --git a/ui/aura/window_tree_host_x11.cc b/ui/aura/window_tree_host_x11.cc
index 0635b7a65ff21e4b22f58649ced937e831269c81..d57358cf49a837d9a30ecdb6af3b4e1c749cb640 100644
--- a/ui/aura/window_tree_host_x11.cc
+++ b/ui/aura/window_tree_host_x11.cc
@@ -252,9 +252,6 @@ uint32_t WindowTreeHostX11::DispatchEvent(const ui::PlatformEvent& event) {
                     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);