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

third_party/WebKit/Source/core/css/CSSPrimitiveValueMappings.h

 /*
  * Copyright (C) 2007 Alexey Proskuryakov <ap@nypop.com>.
  * Copyright (C) 2008, 2009, 2010, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (C) 2009 Jeff Schiller <codedread@gmail.com>
  * Copyright (C) Research In Motion Limited 2010. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
@@ skipping 2611 matching lines @@
     case CSSValueKeepAll:
         return KeepAllWordBreak;
     default:
         break;
     }
 
     ASSERT_NOT_REACHED();
     return NormalWordBreak;
 }
 
+template<> inline CSSPrimitiveValue::CSSPrimitiveValue(EOverflowAnchor e)
+    : CSSValue(PrimitiveClass)
+{
+    init(UnitType::ValueID);
+    switch (e) {
+    case AnchorVisible:
+        m_value.valueID = CSSValueVisible;
+        break;
+    case AnchorNone:
+        m_value.valueID = CSSValueNone;
+        break;
+    case AnchorAuto:
+        m_value.valueID = CSSValueAuto;
+        break;
+    }
+}
+
+template<> inline EOverflowAnchor CSSPrimitiveValue::convertTo() const
+{
+    DCHECK(isValueID());
+    switch (m_value.valueID) {
+    case CSSValueVisible:
+        return AnchorVisible;
+    case CSSValueNone:
+        return AnchorNone;
+    case CSSValueAuto:
+        return AnchorAuto;
+    default:
+        break;
+    }
+
+    NOTREACHED();
+    return AnchorNone;
+}
+
 template<> inline CSSPrimitiveValue::CSSPrimitiveValue(EOverflowWrap e)
     : CSSValue(PrimitiveClass)
 {
     init(UnitType::ValueID);
     switch (e) {
     case NormalOverflowWrap:
         m_value.valueID = CSSValueNormal;
         break;
     case BreakOverflowWrap:
         m_value.valueID = CSSValueBreakWord;
@@ skipping 2027 matching lines @@
     default:
         break;
     }
     ASSERT_NOT_REACHED();
     return ContainsNone;
 }
 
 } // namespace blink
 
 #endif