Currently macOS apps made with Flutter require a click to activate the window first, then another click to click on a button.

Most of the time this is what you want, but some apps (like floating utility apps) need the first click to activate the window and send the click to Flutter.

Also if you have a custom drag area in your Flutter window, you need the ability to click and drag un-active windows.

Inside FlutterView.mm we need a way to enable this:

• (BOOL)acceptsFirstMouse:(NSEvent*)event {
  return YES;
  }

I compiled the engine and testing this and it works. But probably not everyone will want "YES" so we need a way to turn this on or off.