Implement bounce suppression in ScrollAnchor.

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 2740 matching lines @@
 {
     PaintLayer* layer = nullptr;
     if (LayoutObject* parent = layoutObject->parent())
         layer = parent->enclosingLayer();
     bool found = false;
 
     // Walk up the layer tree to clear any scroll anchors that reference us.
     while (layer) {
         if (PaintLayerScrollableArea* scrollableArea = layer->getScrollableArea()) {
             ScrollAnchor& anchor = scrollableArea->scrollAnchor();
-            if (anchor.anchorObject() == layoutObject) {
+            if (anchor.refersTo(layoutObject)) {
                 found = true;
                 if (behavior == Clear)
-                    anchor.clear();
+                    anchor.notifyRemoved(layoutObject);
                 else
                     return true;
             }
         }
         layer = layer->parent();
     }
     if (FrameView* view = layoutObject->frameView()) {
         ScrollAnchor& anchor = view->scrollAnchor();
-        if (anchor.anchorObject() == layoutObject) {
+        if (anchor.refersTo(layoutObject)) {
             found = true;
             if (behavior == Clear)
-                anchor.clear();
+                anchor.notifyRemoved(layoutObject);
         }
     }
     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.
@@ skipping 903 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