Always call UpdateCompositedScrollOffset, not just for the root layer

Bug: 927560
Change-Id: I1d5522aae4f11dd3f5b8947bb089bac1bf19bdb4
Reviewed-on: https://chromium-review.googlesource.com/c/1452701
Reviewed-by: Chris Harrelson <chrishtr@chromium.org>
Commit-Queue: Mason Freed <masonfreed@chromium.org>
Cr-Commit-Position: refs/heads/master@{#628942}
IntRect PaintLayerScrollableArea::ScrollCornerRect() const {
  bool has_horizontal_bar = HorizontalScrollbar();
  bool has_vertical_bar = VerticalScrollbar();
  bool has_resizer = GetLayoutBox()->StyleRef().Resize() != EResize::kNone;
  if ((has_horizontal_bar && has_vertical_bar) ||
      (has_resizer && (has_horizontal_bar || has_vertical_bar))) {
    return CornerRect(GetLayoutBox()->PixelSnappedBorderBoxRect(
        Layer()->SubpixelAccumulation()));
  }
  return IntRect();
}

IntRect PaintLayerScrollableArea::ScrollCornerRect() const {
  bool has_horizontal_bar = HorizontalScrollbar();
  bool has_vertical_bar = VerticalScrollbar();
  bool has_resizer = GetLayoutBox()->StyleRef().Resize() != EResize::kNone;
  if ((has_horizontal_bar && has_vertical_bar) ||
      (has_resizer && (has_horizontal_bar || has_vertical_bar))) {
    return CornerRect(GetLayoutBox()->PixelSnappedBorderBoxRect(
        Layer()->SubpixelAccumulation()));
  }
  return IntRect();
}
