Reviewed by Dan Bernstein.

        https://bugs.webkit.org/show_bug.cgi?id=22215
        Avoid calling absoluteClippedOverflowRect() so many times

        RenderLayer::updateLayerPositions() computes the clipped overflow rect
        and the outline bounds for repaint, and then calls repaintAfterLayoutIfNeeded()
        which can compute the same rects all over again. Avoid this by passing
        these two rects into repaintAfterLayoutIfNeeded() if known. This measurably
        reduces the time spent in updateLayerPositions() for some content.

        * rendering/RenderLayer.cpp:
        (WebCore::RenderLayer::updateLayerPositions):
        * rendering/RenderObject.cpp:
        (WebCore::RenderObject::repaintAfterLayoutIfNeeded):
        * rendering/RenderObject.h:

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@55065 268f45cc-cd09-0410-ab3c-d52691b4dbfc