@Override
  public void getRootBounds(RectF bounds) {
    if (mTransformCallback != null) {
      mTransformCallback.getRootBounds(bounds);
    } else {
      bounds.set(getBounds());
    }
  }
As {@code setCurrent}, but without invalidating a drawable. Subclasses are responsible to call
{@code invalidateSelf} on their own.

@param newDelegate
@return the previous delegate
drawee/src/main/java/com/facebook/drawee/drawable/ForwardingDrawable.java