Test that setting scrollTop on an overflow:scroll element works with both scroll behaviors

This is a testharness.js-based test.
PASS Scroll x:0, y:2, smooth:false 
PASS Scroll x:0, y:4, smooth:false 
PASS Scroll x:0, y:25, smooth:true 
PASS Scroll x:0, y:45, smooth:true 
PASS Scroll x:0, y:4100, smooth:true 
PASS Scroll x:0, y:20, smooth:true 
Harness: the test ran to completion.