[Repaint-After-Layout] Enable by default on release.

This Cl re-enables Repaint-After-Layout as the default.

BUG=371856,320139

Review URL: https://codereview.chromium.org/311873002

git-svn-id: svn://svn.chromium.org/blink/trunk@175429 bbb929c8-8fbe-4397-9dbb-9b2b20218538