Revert "Fire onscroll events at requestAnimationFrame timing"

This reverts commit bee9e5782cbc0b1fa34cc8581941c6f94ca80995.

Conflicts:
        Source/core/dom/Document.cpp

BUG=306179

Review URL: https://codereview.chromium.org/26883004

git-svn-id: svn://svn.chromium.org/blink/trunk@159372 bbb929c8-8fbe-4397-9dbb-9b2b20218538