Use ScrollAnchor in FrameView and PaintLayerScrollableArea.

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

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2000 Dirk Mueller (mueller@kde.org)
  *           (C) 2004 Allan Sandfeld Jensen (kde@carewolf.com)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2009 Google Inc. All rights reserved.
  * Copyright (C) 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  *
  * This library is free software; you can redistribute it and/or
@@ skipping 2626 matching lines @@
             layer->dirtyVisibleContentStatus();
     }
 
     if (parent()->childrenInline())
         parent()->dirtyLinesFromChangedChild(this);
 
     if (LayoutFlowThread* flowThread = flowThreadContainingBlock())
         flowThread->flowThreadDescendantWasInserted(this);
 }
 
+enum FindReferencingScrollAnchorsBehavior {
+    DontClear,
+    Clear
+};
+
+static bool findReferencingScrollAnchors(LayoutObject* layoutObject, FindReferencingScrollAnchorsBehavior behavior)
+{
+    PaintLayer* layer = layoutObject->enclosingLayer();
+    bool found = false;
+
+    // Walk up the layer tree to clear any scroll anchors that reference us.
+    while (layer) {
+        if (PaintLayerScrollableArea* scrollableArea = layer->scrollableArea()) {
+            ScrollAnchor& anchor = scrollableArea->scrollAnchor();
+            if (anchor.anchorObject() == layoutObject) {
+                found = true;
+                if (behavior == Clear)
+                    anchor.clear();
+                else
+                    return true;
+            }
+        }
+        layer = layer->parent();
+    }
+    if (FrameView* view = layoutObject->frameView()) {
+        ScrollAnchor& anchor = view->scrollAnchor();
+        if (anchor.anchorObject() == layoutObject) {
+            found = true;
+            if (behavior == Clear)
+                anchor.clear();
+        }
+    }
+    return found;
+}
+
 void LayoutObject::willBeRemovedFromTree()
 {
     // FIXME: We should ASSERT(isRooted()) but we have some out-of-order removals which would need to be fixed first.
 
     // If we remove a visible child from an invisible parent, we don't know the layer visibility any more.
     PaintLayer* layer = nullptr;
     if (parent()->style()->visibility() != VISIBLE && style()->visibility() == VISIBLE && !hasLayer()) {
         layer = parent()->enclosingLayer();
         if (layer)
             layer->dirtyVisibleContentStatus();
     }
 
     // Keep our layer hierarchy updated.
     if (slowFirstChild() || hasLayer()) {
         if (!layer)
             layer = parent()->enclosingLayer();
         removeLayers(layer);
     }
 
     if (isOutOfFlowPositioned() && parent()->childrenInline())
         parent()->dirtyLinesFromChangedChild(this);
 
     removeFromLayoutFlowThread();
 
     // Update cached boundaries in SVG layoutObjects if a child is removed.
     if (parent()->isSVG())
         parent()->setNeedsBoundariesUpdate();
+
+    if (RuntimeEnabledFeatures::scrollAnchoringEnabled() && m_bitfields.isScrollAnchorObject()) {
+        // Clear the bit first so that anchor.clear() doesn't recurse into findReferencingScrollAnchors.
+        m_bitfields.setIsScrollAnchorObject(false);
+        findReferencingScrollAnchors(this, Clear);
+    }
+}
+
+void LayoutObject::maybeClearIsScrollAnchorObject()
+{
+    if (m_bitfields.isScrollAnchorObject())
+        m_bitfields.setIsScrollAnchorObject(findReferencingScrollAnchors(this, DontClear));
 }
 
 void LayoutObject::removeFromLayoutFlowThread()
 {
     if (!isInsideFlowThread())
         return;
 
     // Sometimes we remove the element from the flow, but it's not destroyed at that time.
     // It's only until later when we actually destroy it and remove all the children from it.
     // Currently, that happens for firstLetter elements and list markers.
@@ skipping 884 matching lines @@
         const blink::LayoutObject* root = object1;
         while (root->parent())
             root = root->parent();
         root->showLayoutTreeAndMark(object1, "*", object2, "-", 0);
     } else {
         fprintf(stderr, "Cannot showLayoutTree. Root is (nil)\n");
     }
 }
 
 #endif