[Android] Implement onShowCustomView and add test case.

1. Implement onShowCustomView with requested orientation.
2. Add test case for onShow/HideCustomView.
bad indent for the third condition, suggest
```
if (requestedOrientation != orientation &&
    requestedOrientation >= ActivityInfo.SCREEN_ORIENTATION_UNSPECIFIED &&
    requestedOrientation <= ActivityInfo.SCREEN_ORIENTATION_LOCKED) {
```