@Override
  @Nullable
  public Drawable setDrawable(@Nullable Drawable newDrawable) {
    return setCurrent(newDrawable);
  }
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