Changes

This test is identical to tscrollx, but it scrolls the 50 pages of the tp5o set (rather than 6 synthetic pages which tscrollx scrolls). For There are two variants for each test page, the test . The "regular" variant waits 500ms after the page load event fires, then iterates 100 scroll steps of 10px each (or until the bottom of the page is reached - whichever comes first), then reports the average frame interval. The "CSSOM" variant is similar, but uses APZ's smooth scrolling mechanism to do compositor scrolling instead of main-thread scrolling. So it just requests the final scroll destination and the compositor handles the scrolling and reports frame intervals.