Behavior regression between platform plugins on Android on when calling show()

When calling show() on a window and using the GL-based platform plugin on Android, the window will correctly be shown in fullscreen because the EGLFS superclass implements the ShowIsFullscreen style hint. However, this is missing from the raster based plugin, so behavior will be different based on somewhat arbitrary parameters and pure widget-based apps will be not fill the screen by default, requiring platform-specific code to make it work correctly.