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}
void PaintLayerScrollableArea::DidChangeGlobalRootScroller() {
  if (GetLayoutBox()->GetNode()->IsElementNode()) {
    ToElement(GetLayoutBox()->GetNode())->SetNeedsCompositingUpdate();
    GetLayoutBox()->SetNeedsPaintPropertyUpdate();
  }

  if (GetLayoutBox()->GetFrame()->GetSettings() &&
      GetLayoutBox()->GetFrame()->GetSettings()->GetViewportEnabled()) {
    bool needs_horizontal_scrollbar;
    bool needs_vertical_scrollbar;
    ComputeScrollbarExistence(needs_horizontal_scrollbar,
                              needs_vertical_scrollbar);
    SetHasHorizontalScrollbar(needs_horizontal_scrollbar);
    SetHasVerticalScrollbar(needs_vertical_scrollbar);
  }
}

void PaintLayerScrollableArea::DidChangeGlobalRootScroller() {
  if (GetLayoutBox()->GetNode()->IsElementNode()) {
    ToElement(GetLayoutBox()->GetNode())->SetNeedsCompositingUpdate();
    GetLayoutBox()->SetNeedsPaintPropertyUpdate();
  }

  if (GetLayoutBox()->GetFrame()->GetSettings() &&
      GetLayoutBox()->GetFrame()->GetSettings()->GetViewportEnabled()) {
    bool needs_horizontal_scrollbar;
    bool needs_vertical_scrollbar;
    ComputeScrollbarExistence(needs_horizontal_scrollbar,
                              needs_vertical_scrollbar);
    SetHasHorizontalScrollbar(needs_horizontal_scrollbar);
    SetHasVerticalScrollbar(needs_vertical_scrollbar);
  }
}
