private void adjustTopByAspectRatio(RectF rect, float aspectRatio) {
    rect.top = rect.bottom - rect.width() / aspectRatio;
  }
Adjust top edge by current crop window width and the given aspect ratio, the bottom edge
remains in possition while the top adjusts to keep aspect ratio to the width.
core/src/main/java/com/theartofdev/edmodo/cropper/CropWindowMoveHandler.java