ScrollBar not resizing to left correctly when window is extended left

When a Scrollbar's size is set to scale inversely with window size directly or indirectly, if the window is resized to the left the size of the scrollbar does not update correctly. Clicking the scrollbar after resizing the window results in the scrollbar instantly resizing to the correct size.

Steps to reproduce:

1. Run the attached example
2. Move the scroll bar to the right side of the window
3. Increase the size of the window by resizing the left edge