Make img referrerpolicy attribute runtime-enabled

Source/core/html/HTMLImageElement.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2010 Apple Inc. All rights reserved.
  * Copyright (C) 2010 Google Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
@@ skipping 252 matching lines @@
         if (userAgentShadowRoot()) {
             Element* text = userAgentShadowRoot()->getElementById("alttext");
             String value = altText();
             if (text && text->textContent() != value)
                 text->setTextContent(altText());
         }
     } else if (name == srcAttr || name == srcsetAttr || name == sizesAttr) {
         selectSourceURL(ImageLoader::UpdateIgnorePreviousError);
     } else if (name == usemapAttr) {
         setIsLink(!value.isNull());
-    } else if (name == referrerpolicyAttr) {
+    } else if (RuntimeEnabledFeatures::referrerPolicyAttributeEnabled() && name == referrerpolicyAttr) {
         m_referrerPolicy = ReferrerPolicyDefault;
         if (!value.isNull())
             SecurityPolicy::referrerPolicyFromString(value, &m_referrerPolicy);
     } else {
         HTMLElement::parseAttribute(name, value);
     }
 }
 
 String HTMLImageElement::altText() const
 {
@@ skipping 475 matching lines @@
     ensureUserAgentShadowRoot();
 }
 
 bool HTMLImageElement::isOpaque() const
 {
     Image* image = const_cast<HTMLImageElement*>(this)->imageContents();
     return image && image->currentFrameKnownToBeOpaque();
 }
 
 }