[DNS] Don't adjust the scroll position if the anchor element changes in size

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/LayoutView.h"
 #include "core/layout/line/InlineTextBox.h"
@@ skipping 145 matching lines @@
     }
     if (m_anchorObject)
         return;
 
     findAnchor();
     if (!m_anchorObject)
         return;
 
     m_anchorObject->setIsScrollAnchorObject();
     m_savedRelativeOffset = computeRelativeOffset(m_anchorObject, m_scroller, m_corner);
+    m_savedAnchorSize =  toLayoutBox(m_anchorObject)->size();
 }
 
 void ScrollAnchor::restore()
 {
     if (!m_anchorObject)
         return;
 
+    if (toLayoutBox(m_anchorObject)->size() != m_savedAnchorSize) {
+        clear();
+        return;
+    }
+
     LayoutSize adjustment = computeRelativeOffset(m_anchorObject, m_scroller, m_corner) - m_savedRelativeOffset;
     if (!adjustment.isZero()) {
         m_scroller->setScrollPosition(
             m_scroller->scrollPositionDouble() + DoubleSize(adjustment),
             AnchoringScroll);
         // Update UMA metric.
         DEFINE_STATIC_LOCAL(EnumerationHistogram, adjustedOffsetHistogram,
             ("Layout.ScrollAnchor.AdjustedScrollOffset", 2));
         adjustedOffsetHistogram.count(1);
         UseCounter::count(scrollerLayoutBox(m_scroller)->document(), UseCounter::ScrollAnchored);
     }
 }
 
 void ScrollAnchor::clear()
 {
     LayoutObject* anchorObject = m_anchorObject;
     m_anchorObject = nullptr;
 
     if (anchorObject)
         anchorObject->maybeClearIsScrollAnchorObject();
 }
 
 } // namespace blink