Record the old and new layout rects into RenderObject.

As we walk the layout tree, record the old/new layout rects into the object.
The old rect is only stored if it has not been set for this layout pass already.

BUG=310398

Review URL: https://codereview.chromium.org/49323004

git-svn-id: svn://svn.chromium.org/blink/trunk@161258 bbb929c8-8fbe-4397-9dbb-9b2b20218538