Revert "Revert "Move some scroll invalidations to the paint invalidation phase""

This reverts commit 9cd85241c98a725b9fdd2d9923137a77cf4aeb8a.

The revert did not fix the mac pixel tests

BUG=
TBR=keishi, jchaffraix@chromium.org

Review URL: https://codereview.chromium.org/544203004

git-svn-id: svn://svn.chromium.org/blink/trunk@181486 bbb929c8-8fbe-4397-9dbb-9b2b20218538