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* maybeStickyAncestor = from;
   while (maybeStickyAncestor && maybeStickyAncestor != to) {
-    if (maybeStickyAncestor->isStickyPositioned()) {
+    if (maybeStickyAncestor->style()->hasStickyConstrainedPosition()) {
       return toLayoutBoxModelObject(maybeStickyAncestor);
     }
 
     maybeStickyAncestor =
         maybeStickyAncestor->isLayoutInline()
             ? maybeStickyAncestor->containingBlock()
             : toLayoutBox(maybeStickyAncestor)->locationContainer();
   }
   return nullptr;
 }
@@ skipping 154 matching lines @@
   ImageQualityController::remove(*this);
 
   // A continuation of this LayoutObject should be destroyed at subclasses.
   ASSERT(!continuation());
 
   if (isPositioned()) {
     // Don't use this->view() because the document's layoutView has been set to
     // 0 during destruction.
     if (LocalFrame* frame = this->frame()) {
       if (FrameView* frameView = frame->view()) {
-        if (style()->hasViewportConstrainedPosition())
+        if (style()->hasViewportConstrainedPosition() ||
+            style()->hasStickyConstrainedPosition())
           frameView->removeViewportConstrainedObject(*this);
       }
     }
   }
 
   LayoutObject::willBeDestroyed();
 
   destroyLayer();
 }
 
@@ skipping 160 matching lines @@
         bodyLayout->setShouldDoFullPaintInvalidation();
       }
     }
   }
 
   if (FrameView* frameView = view()->frameView()) {
     bool newStyleIsViewportConstained =
         style()->position() == EPosition::kFixed;
     bool oldStyleIsViewportConstrained =
         oldStyle && oldStyle->position() == EPosition::kFixed;
-    bool newStyleIsSticky = style()->position() == EPosition::kSticky;
+    bool newStyleIsSticky = style()->hasStickyConstrainedPosition();
     bool oldStyleIsSticky =
-        oldStyle && oldStyle->position() == EPosition::kSticky;
+        oldStyle && oldStyle->hasStickyConstrainedPosition();
 
     if (newStyleIsSticky != oldStyleIsSticky) {
       if (newStyleIsSticky) {
         // 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 600 matching lines @@
     constraints.addAnchorEdge(
         StickyPositionScrollingConstraints::AnchorEdgeTop);
   }
 
   if (!style()->bottom().isAuto() && !skipBottom) {
     constraints.setBottomOffset(minimumValueForLength(
         style()->bottom(), LayoutUnit(constrainingSize.height())));
     constraints.addAnchorEdge(
         StickyPositionScrollingConstraints::AnchorEdgeBottom);
   }
+  // At least one edge should be anchored if we are calculating constraints.
+  DCHECK(constraints.anchorEdges());
   scrollableArea->stickyConstraintsMap().set(layer(), constraints);
 }
 
 FloatRect LayoutBoxModelObject::computeStickyConstrainingRect() const {
   if (layer()->ancestorOverflowLayer()->isRootLayer())
     return view()->frameView()->visibleContentRect();
 
   LayoutBox* enclosingClippingBox =
       layer()->ancestorOverflowLayer()->layoutBox();
   DCHECK(enclosingClippingBox);
@@ skipping 402 matching lines @@
   if (rootElementStyle->hasBackground())
     return false;
 
   if (node() != document().firstBodyElement())
     return false;
 
   return true;
 }
 
 }  // namespace blink