[SPv2] FrameView::synchronizedPaint should apply root property nodes

The root property nodes weren't applied because we expect the PaintLayer of
the root LayoutView to apply them before painting. However in debug builds
the GraphicsLayer could paint debug background before we ever reach the
PaintLayer. Also the scrollbar layers (not implemented in SPv2. Upcoming.)
are not backed by PaintLayer.

Review-Url: https://codereview.chromium.org/2140173004
Cr-Commit-Position: refs/heads/master@{#405080}
5 files changed