Rename repaint to paintInvalidation in core/rendering/compositing.

This CL removes the use of repaint in core/rendering/compositing in favour
of paintInvalidation.

BUG=338691

Review URL: https://codereview.chromium.org/468343002

git-svn-id: svn://svn.chromium.org/blink/trunk@180209 bbb929c8-8fbe-4397-9dbb-9b2b20218538