Reenable the commnted out test expectation

BUG=414283
TBR=rbyers@chromium.org

Review URL: https://codereview.chromium.org/642953002

git-svn-id: svn://svn.chromium.org/blink/trunk@183503 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Make compositor and blink talk in fractional scroll offset

Make the WebLayer scrolling interface setScrollPositionDouble() and
scrollPositionDouble() to use WebDoublePoint so that compositor and
blink are both using fractional scroll offset.

This enables document fractional scroll on main thread.

BUG=414283

Review URL: https://codereview.chromium.org/629583002

git-svn-id: svn://svn.chromium.org/blink/trunk@183504 bbb929c8-8fbe-4397-9dbb-9b2b20218538