[RLS] Don't add to ScrollableAreaSet if the size is zero

third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011, 2012 Apple Inc. All rights
  * reserved.
  *
  * Portions are Copyright (C) 1998 Netscape Communications Corporation.
  *
  * Other contributors:
  *   Robert O'Callahan <roc+@cs.cmu.edu>
  *   David Baron <dbaron@fas.harvard.edu>
  *   Christian Biesinger <cbiesinger@gmail.com>
@@ skipping 893 matching lines @@
   if (!scrollbars_are_frozen && HasOverlayScrollbars()) {
     if (!ScrollSize(kHorizontalScrollbar))
       SetHasHorizontalScrollbar(false);
     if (!ScrollSize(kVerticalScrollbar))
       SetHasVerticalScrollbar(false);
   }
 
   ClampScrollOffsetAfterOverflowChange();
 
   if (!scrollbars_are_frozen) {
-    UpdateScrollableAreaSet(HasScrollableHorizontalOverflow() ||
-                            HasScrollableVerticalOverflow());
+    UpdateScrollableAreaSet();
   }
 
   DisableCompositingQueryAsserts disabler;
   PositionOverflowControls();
 
   Node* node = Box().GetNode();
   if (isHTMLSelectElement(node))
     toHTMLSelectElement(node)->ScrollToOptionAfterLayout(*this);
 }
 
@@ skipping 81 matching lines @@
   int client_width = PixelSnappedClientSize().Width();
   if (NeedsRelayout() && !HadVerticalScrollbarBeforeRelayout())
     client_width += VerticalScrollbarWidth();
   return PixelSnappedScrollWidth() > client_width;
 }
 
 bool PaintLayerScrollableArea::HasVerticalOverflow() const {
   return PixelSnappedScrollHeight() > PixelSnappedClientSize().Height();
 }
 
-bool PaintLayerScrollableArea::HasScrollableHorizontalOverflow() const {
-  return HasHorizontalOverflow() && Box().ScrollsOverflowX();
-}
-
-bool PaintLayerScrollableArea::HasScrollableVerticalOverflow() const {
-  return HasVerticalOverflow() && Box().ScrollsOverflowY();
-}
-
 // This function returns true if the given box requires overflow scrollbars (as
 // opposed to the 'viewport' scrollbars managed by the PaintLayerCompositor).
 // FIXME: we should use the same scrolling machinery for both the viewport and
 // overflow. Currently, we need to avoid producing scrollbars here if they'll be
 // handled externally in the RLC.
 static bool CanHaveOverflowScrollbars(const LayoutBox& box) {
   return (RuntimeEnabledFeatures::RootLayerScrollingEnabled() ||
           !box.IsLayoutView()) &&
          box.GetDocument().ViewportDefiningElement() != box.GetNode();
 }
 
 void PaintLayerScrollableArea::UpdateAfterStyleChange(
     const ComputedStyle* old_style) {
   // Don't do this on first style recalc, before layout has ever happened.
   if (!OverflowRect().Size().IsZero()) {
-    UpdateScrollableAreaSet(HasScrollableHorizontalOverflow() ||
-                            HasScrollableVerticalOverflow());
+    UpdateScrollableAreaSet();
   }
 
   // Whenever background changes on the scrollable element, the scroll bar
   // overlay style might need to be changed to have contrast against the
   // background.
   // Skip the need scrollbar check, because we dont know do we need a scrollbar
   // when this method get called.
   Color old_background;
   if (old_style) {
     old_background =
@@ skipping 770 matching lines @@
   LayoutRect visible_rect(LayoutPoint(), ClientSize());
   LayoutRect intersect =
       LocalToAbsolute(Box(), Intersection(visible_rect, local_expose_rect));
   if (intersect.IsEmpty() && !visible_rect.IsEmpty() &&
       !local_expose_rect.IsEmpty()) {
     return LocalToAbsolute(Box(), local_expose_rect);
   }
   return intersect;
 }
 
-void PaintLayerScrollableArea::UpdateScrollableAreaSet(bool has_overflow) {
+void PaintLayerScrollableArea::UpdateScrollableAreaSet() {
   LocalFrame* frame = Box().GetFrame();
   if (!frame)
     return;
 
   LocalFrameView* frame_view = frame->View();
   if (!frame_view)
     return;
 
+  bool has_overflow = !Box().Size().IsZero() &&
+                      ((HasHorizontalOverflow() && Box().ScrollsOverflowX()) ||
+                       (HasVerticalOverflow() && Box().ScrollsOverflowY()));
+
   bool is_visible_to_hit_test = Box().Style()->VisibleToHitTesting();
   bool did_scroll_overflow = scrolls_overflow_;
   if (Box().IsLayoutView()) {
     ScrollbarMode h_mode;
     ScrollbarMode v_mode;
     ToLayoutView(Box()).CalculateScrollbarModes(h_mode, v_mode);
     if (h_mode == kScrollbarAlwaysOff && v_mode == kScrollbarAlwaysOff)
       has_overflow = false;
   }
   scrolls_overflow_ = has_overflow && is_visible_to_hit_test;
@@ skipping 409 matching lines @@
 
 void PaintLayerScrollableArea::DelayScrollOffsetClampScope::
     ClampScrollableAreas() {
   for (auto& scrollable_area : *needs_clamp_)
     scrollable_area->ClampScrollOffsetAfterOverflowChange();
   delete needs_clamp_;
   needs_clamp_ = nullptr;
 }
 
 }  // namespace blink