[SPInvaldation] Update subtree paint properties when a layout subtree is inserted

Add LayoutObject::subtreeNeedsPaintPropertyUpdate() and set it in
LayoutObjectChildList::addChild() to force paint property update of the
whole subtree.

BUG=645667
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_layout_tests_slimming_paint_v2

Review-Url: https://codereview.chromium.org/2585603002
Cr-Commit-Position: refs/heads/master@{#439193}
5 files changed