Remove Overlay Scrollbar if not scrollable along the axis

Remove Overlay Scrollbar if not scrollable along that axis. If the 
scrollSize along that axis is zero then set scrollbar along that
axis to false. This is applicable to Solid-Color scrollbars in Android
& Overlay scrollbars in the Aura.

BUG=415031

Review URL: https://codereview.chromium.org/643933002

git-svn-id: svn://svn.chromium.org/blink/trunk@183641 bbb929c8-8fbe-4397-9dbb-9b2b20218538