Combine layout-triggered repaint paths of layered and non-layered RenderObjects

Previously, layered RenderObjects are marked needsFullRepaint in
setNeedsLayout(), while other objects check repaint after layout.

The code path of the former is very old
(http://trac.webkit.org/changeset/21390):
   "The only catch is that we cannot rely on its 'do a full repaint
    if the object needs layout' behavior, since by the time we call it,
    the needs layout flag has been reset. The solution is to cache the
    need for a full repaint in the layer."

However, "caching the need for a full repaint in the layer" became
unnecessary after WebKit has LayoutRepainter.

Combine the repaint paths of layered and non-layered RenderObjects.

BUG=325569

Review URL: https://codereview.chromium.org/219893003

git-svn-id: svn://svn.chromium.org/blink/trunk@173156 bbb929c8-8fbe-4397-9dbb-9b2b20218538