Only create sticky position constraints for constrained sticky position.

third_party/WebKit/Source/core/layout/LayoutBoxModelObject.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2005 Allan Sandfeld Jensen (kde@carewolf.com)
  *           (C) 2005, 2006 Samuel Weinig (sam.weinig@gmail.com)
  * Copyright (C) 2005, 2006, 2007, 2008, 2009 Apple Inc. All rights reserved.
  * Copyright (C) 2010 Google Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
@@ skipping 56 matching lines @@
     return nullptr;
 
   return &it->value;
 }
 
 // Inclusive of |from|, exclusive of |to|.
 LayoutBoxModelObject* FindFirstStickyBetween(LayoutObject* from,
                                              LayoutObject* to) {
   LayoutObject* maybe_sticky_ancestor = from;
   while (maybe_sticky_ancestor && maybe_sticky_ancestor != to) {
-    if (maybe_sticky_ancestor->IsStickyPositioned()) {
+    if (maybe_sticky_ancestor->Style()->HasStickyConstrainedPosition()) {
       return ToLayoutBoxModelObject(maybe_sticky_ancestor);
     }
 
     maybe_sticky_ancestor =
         maybe_sticky_ancestor->IsLayoutInline()
             ? maybe_sticky_ancestor->Container()
             : ToLayoutBox(maybe_sticky_ancestor)->LocationContainer();
   }
   return nullptr;
 }
@@ skipping 154 matching lines @@
   ImageQualityController::Remove(*this);
 
   // A continuation of this LayoutObject should be destroyed at subclasses.
   DCHECK(!Continuation());
 
   if (IsPositioned()) {
     // Don't use this->view() because the document's layoutView has been set to
     // 0 during destruction.
     if (LocalFrame* frame = this->GetFrame()) {
       if (FrameView* frame_view = frame->View()) {
-        if (Style()->HasViewportConstrainedPosition())
+        if (Style()->HasViewportConstrainedPosition() ||
+            Style()->HasStickyConstrainedPosition())
           frame_view->RemoveViewportConstrainedObject(*this);
       }
     }
   }
 
   LayoutObject::WillBeDestroyed();
 
   DestroyLayer();
 }
 
@@ skipping 163 matching lines @@
         body_layout->SetShouldDoFullPaintInvalidation();
       }
     }
   }
 
   if (FrameView* frame_view = View()->GetFrameView()) {
     bool new_style_is_viewport_constained =
         Style()->GetPosition() == EPosition::kFixed;
     bool old_style_is_viewport_constrained =
         old_style && old_style->GetPosition() == EPosition::kFixed;
-    bool new_style_is_sticky = Style()->GetPosition() == EPosition::kSticky;
+    bool new_style_is_sticky = Style()->HasStickyConstrainedPosition();
     bool old_style_is_sticky =
-        old_style && old_style->GetPosition() == EPosition::kSticky;
+        old_style && old_style->HasStickyConstrainedPosition();
 
     if (new_style_is_sticky != old_style_is_sticky) {
       if (new_style_is_sticky) {
         // During compositing inputs update we'll have the scroll ancestor
         // without having to walk up the tree and can compute the sticky
         // position constraints then.
         if (Layer())
           Layer()->SetNeedsCompositingInputsUpdate();
 
         // TODO(pdr): When slimming paint v2 is enabled, we will need to
@@ skipping 605 matching lines @@
     constraints.AddAnchorEdge(
         StickyPositionScrollingConstraints::kAnchorEdgeTop);
   }
 
   if (!Style()->Bottom().IsAuto() && !skip_bottom) {
     constraints.SetBottomOffset(MinimumValueForLength(
         Style()->Bottom(), LayoutUnit(constraining_size.Height())));
     constraints.AddAnchorEdge(
         StickyPositionScrollingConstraints::kAnchorEdgeBottom);
   }
+  // At least one edge should be anchored if we are calculating constraints.
+  DCHECK(constraints.GetAnchorEdges());
   scrollable_area->GetStickyConstraintsMap().Set(Layer(), constraints);
 }
 
 FloatRect LayoutBoxModelObject::ComputeStickyConstrainingRect() const {
   if (Layer()->AncestorOverflowLayer()->IsRootLayer())
     return View()->GetFrameView()->VisibleContentRect();
 
   LayoutBox* enclosing_clipping_box =
       Layer()->AncestorOverflowLayer()->GetLayoutBox();
   DCHECK(enclosing_clipping_box);
@@ skipping 405 matching lines @@
   if (root_element_style->HasBackground())
     return false;
 
   if (GetNode() != GetDocument().FirstBodyElement())
     return false;
 
   return true;
 }
 
 }  // namespace blink