Implement the overflow-anchor CSS property as an opt-out for ScrollAnchoring

third_party/WebKit/Source/core/css/ComputedStyleCSSValueMapping.cpp

 /*
  * Copyright (C) 2004 Zack Rusin <zack@kde.org>
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2007 Alexey Proskuryakov <ap@webkit.org>
  * Copyright (C) 2007 Nicholas Shanks <webkit@nickshanks.com>
  * Copyright (C) 2011 Sencha, Inc. All rights reserved.
  * Copyright (C) 2015 Google Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
@@ skipping 2144 matching lines @@
     case CSSPropertyOutlineOffset:
         return zoomAdjustedPixelValue(style.outlineOffset(), style);
     case CSSPropertyOutlineStyle:
         if (style.outlineStyleIsAuto())
             return CSSPrimitiveValue::createIdentifier(CSSValueAuto);
         return CSSPrimitiveValue::create(style.outlineStyle());
     case CSSPropertyOutlineWidth:
         return zoomAdjustedPixelValue(style.outlineWidth(), style);
     case CSSPropertyOverflow:
         return CSSPrimitiveValue::create(max(style.overflowX(), style.overflowY()));
+    case CSSPropertyOverflowAnchor:
+        return CSSPrimitiveValue::create(style.overflowAnchor());
     case CSSPropertyOverflowWrap:
         return CSSPrimitiveValue::create(style.overflowWrap());
     case CSSPropertyOverflowX:
         return CSSPrimitiveValue::create(style.overflowX());
     case CSSPropertyOverflowY:
         return CSSPrimitiveValue::create(style.overflowY());
     case CSSPropertyPaddingTop: {
         Length paddingTop = style.paddingTop();
         if (paddingTop.isFixed() || !layoutObject || !layoutObject->isBox())
             return zoomAdjustedPixelValueForLength(paddingTop, style);
@@ skipping 835 matching lines @@
     case CSSPropertyAll:
         return nullptr;
     default:
         break;
     }
     ASSERT_NOT_REACHED();
     return nullptr;
 }
 
 } // namespace blink