Don't show cursor on mouse enter/exit as they can be generated when host window is created/removed.

ui/views/corewm/compound_event_filter.cc

Index: ui/views/corewm/compound_event_filter.cc
diff --git a/ui/views/corewm/compound_event_filter.cc b/ui/views/corewm/compound_event_filter.cc
index 78f988acd9d1ab766a003fc76507ddf0d197867e..418e489f847eae44b6f2596d02fcb63bf6644449 100644
--- a/ui/views/corewm/compound_event_filter.cc
+++ b/ui/views/corewm/compound_event_filter.cc
@@ -169,8 +169,11 @@ void CompoundEventFilter::FilterTouchEvent(ui::TouchEvent* event) {
 void CompoundEventFilter::SetCursorVisibilityOnEvent(aura::Window* target,
                                                      ui::Event* event,
                                                      bool show) {
-  if (event->flags() & ui::EF_IS_SYNTHESIZED)
+  if (event->flags() & ui::EF_IS_SYNTHESIZED ||
+      event->type() == ui::ET_MOUSE_ENTERED ||
+      event->type() == ui::ET_MOUSE_EXITED) {
     return;
+  }
   aura::client::CursorClient* client =
       aura::client::GetCursorClient(target->GetRootWindow());
   if (!client)