Moving the design mode cursor off screen using the positioning controls does not automatically scroll the scene

[sbates-idrc]

Steps to reproduce:

1. Enter custom background design mode
2. Resize the browser window such that the whole scene is not visible
3. Use the positioning controls to move the design mode paintbrush off screen

Expected:

• The scene should be scrolled automatically such that the paintbrush remains visible

Actual:

• The scene is not scrolled