Free the native window's memory after the event were sent for all observers.

If we delete the window immediately other observers may get a invalid
window and cause random crashes.

browser/api/atom_api_window.cc

@@ -61,8 +61,9 @@ void Window::WillCloseWindow(bool* prevent_default) {
 void Window::OnWindowClosed() {
   Emit("closed");
 
-  // Free memory immediately when window is closed.
-  delete this;
+  // Free memory when native window is closed, the delete is delayed so other
+  // observers would not get a invalid pointer of NativeWindow.
+  base::MessageLoop::current()->DeleteSoon(FROM_HERE, this);
 }
 
 void Window::OnWindowBlur() {