[repaint-after-layout] Skip full repaint if the style difference is layout.

Currently in RenderBox::styleWillChange we will issue a view()->repaint() if the
node is the HTML or body element and the diff >= StyleDifferenceRepaint. For
repaint-after-layout, if this is StyleDifferenceLayout, we will do the layout
and end up issuing the same invalidation again.

This CL makes the view()->repaint() call conditional on either
  1) repaint-after-layout is disabled
  2) this is not a StyleDifferenceLayout.

BUG=320139

Review URL: https://codereview.chromium.org/211613002

git-svn-id: svn://svn.chromium.org/blink/trunk@169984 bbb929c8-8fbe-4397-9dbb-9b2b20218538