Content area freezes on "back" swipe gesture

[khimaros]

when i swipe from the edge of the screen to navigate back, approximately one in five times the content area freezes.

the rest of the interface is still responsive and behaves as though it is loading other pages but nothing changes in the content area.

if i then click New Tab, the entire frontend freezes. the only way to recover is to force close the app.

[skyjake]

This is related to #500. Basically, the way the swipe animation is implemented is too complex and cumbersome, and should be rewritten. There are a couple of edge cases where it can malfunction...