Exclude elements with overflow-anchor:none from anchor node selection

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

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "core/layout/ScrollAnchor.h"
 
 #include "core/frame/FrameView.h"
 #include "core/frame/UseCounter.h"
 #include "core/layout/line/InlineTextBox.h"
 #include "core/paint/PaintLayerScrollableArea.h"
@@ skipping 132 matching lines @@
     // developers to reason about the anchor node.
     if (candidate->isAnonymous())
         return ExamineResult(Continue);
 
     if (!candidate->isText() && !candidate->isBox())
         return ExamineResult(Skip);
 
     if (!candidateMayMoveWithScroller(candidate, m_scroller))
         return ExamineResult(Skip);
 
+    if (candidate->style()->overflowAnchor() == AnchorNone)
+        return ExamineResult(Skip);
+
     LayoutRect candidateRect = relativeBounds(candidate, m_scroller);
     LayoutRect visibleRect = scrollerLayoutBoxItem(m_scroller).overflowClipRect(LayoutPoint());
 
     bool occupiesSpace = candidateRect.width() > 0 && candidateRect.height() > 0;
     if (occupiesSpace && visibleRect.intersects(candidateRect)) {
         return ExamineResult(
             visibleRect.contains(candidateRect) ? Return : Constrain,
             cornerFromCandidateRect(candidate));
     } else {
         return ExamineResult(Skip);
@@ skipping 29 matching lines @@
     }
 }
 
 void ScrollAnchor::save()
 {
     DCHECK(m_scroller);
     if (m_scroller->scrollPosition() == IntPoint::zero()) {
         clear();
         return;
     }
+
+    // TODO(ymalik): Just because we have a previously selected anchor doesn't
+    // mean that it's guaranteed to be valid. For e.g. overflow-anchor: none
+    // may have been added after anchor selection. The SANACLAP design poposal
+    // may fix this (see crbug.com/637626).
     if (m_current)
         return;
 
     findAnchor();
     if (!m_current)
         return;
 
     m_current.m_anchorObject->setIsScrollAnchorObject();
     m_current.m_savedRelativeOffset = computeRelativeOffset(
         m_current.m_anchorObject, m_scroller, m_current.m_corner);
@@ skipping 98 matching lines @@
 
 void ScrollAnchor::notifyRemoved(LayoutObject* layoutObject)
 {
     if (m_current.m_anchorObject == layoutObject)
         m_current.clear();
     if (m_lastAdjusted.m_anchorObject == layoutObject)
         m_lastAdjusted.clear();
 }
 
 } // namespace blink