Add a UseCounter for when xml:base takes effect in Element.baseURI

Source/core/dom/Element.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Peter Kelly (pmk@post.com)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  *           (C) 2007 David Smith (catfish.man@gmail.com)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2012, 2013 Apple Inc. All rights reserved.
  *           (C) 2007 Eric Seidel (eric@webkit.org)
  *
  * This library is free software; you can redistribute it and/or
@@ skipping 1194 matching lines @@
 
     if (Element* parent = parentElement())
         return parent->locateNamespacePrefix(namespaceToLocate);
 
     return nullAtom;
 }
 
 KURL Element::baseURI() const
 {
     const AtomicString& baseAttribute = fastGetAttribute(baseAttr);
+    if (!baseAttribute.isEmpty())
+        UseCounter::count(document(), UseCounter::ElementBaseURIFromXMLBase);
+
     KURL base(KURL(), baseAttribute);
     if (!base.protocol().isEmpty())
         return base;
 
     ContainerNode* parent = parentNode();
     if (!parent)
         return base;
 
     const KURL& parentBase = parent->baseURI();
     if (parentBase.isNull())
@@ skipping 2042 matching lines @@
         return wrapper;
 
     CustomElementBinding* binding = perContextData->customElementBinding(customElementDefinition());
 
     wrapper->SetPrototype(binding->prototype());
 
     return V8DOMWrapper::associateObjectWithWrapperNonTemplate(this, wrapperType, wrapper, isolate);
 }
 
 } // namespace blink