code: void wrappedSmoothScrollBy(int dx, int dy) {
          if (!mScrollable) {
              return;
          }
  
          smoothScrollBy(dx, dy);
          if (mLockableScrollChangedListener != null) {
              mLockableScrollChangedListener.onSmoothScrollBy(dx, dy);
          }
      }
docs: Wrapping the {@link HorizontalScrollView#smoothScrollBy(int, int)} function to increase
  testability.
  
  @param dx the number of pixels to scroll by on the X axis
  @param dy the number of pixels to scroll by on the Y axis