Refactor repainting logic to abstract away the specific repaint container.

In basically all cases it was calling containerForRepaint(),
so no need to pass that extra argument.

BUG=370664

Review URL: https://codereview.chromium.org/307713002

git-svn-id: svn://svn.chromium.org/blink/trunk@175015 bbb929c8-8fbe-4397-9dbb-9b2b20218538