If two tabs are open and a page is loading in one tab while you are
scrolling the other tab using the keyboard, then the scrolling stops working
when the first tab stops loading its page.

Steps to reproduce:
1) Open two tabs, both containing http://www.gnomedesktop.com/
2) Press the reload button.
3) Change to the other tab using the mouse.
4) Start scrolling using the arrow Up, arrow Down, space, Page Up or Page 
  Down keys.

Actual result: Scrolling works while the first tab is loading, after that it
stops working.
Expected result: Scrolling should continue working