DOM: Fix "" handling in Node.lookupNamespaceURI().

third_party/WebKit/Source/core/dom/Node.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc. All
  * rights reserved.
  * Copyright (C) 2008 Nokia Corporation and/or its subsidiary(-ies)
  * Copyright (C) 2009 Torch Mobile Inc. All rights reserved.
  * (http://www.torchmobile.com/)
  *
@@ skipping 1222 matching lines @@
       context = parentElement();
       break;
   }
 
   if (!context)
     return nullAtom;
 
   return context->locateNamespacePrefix(namespaceURI);
 }
 
-const AtomicString& Node::lookupNamespaceURI(const String& prefix) const {
+const AtomicString& Node::lookupNamespaceURI(
+    const String& specifiedPrefix) const {
   // Implemented according to
-  // http://www.w3.org/TR/2004/REC-DOM-Level-3-Core-20040407/namespaces-algorithms.html#lookupNamespaceURIAlgo
+  // https://dom.spec.whatwg.org/#dom-node-lookupnamespaceuri
 
-  if (!prefix.isNull() && prefix.isEmpty())
-    return nullAtom;
+  // 1. If prefix is the empty string, then set it to null.
+  String prefix = specifiedPrefix;
+  if (!specifiedPrefix.isNull() && specifiedPrefix.isEmpty())
+    prefix = String();
 
+  // 2. Return the result of running locate a namespace for the context object
+  // using prefix.
+
+  // https://dom.spec.whatwg.org/#locate-a-namespace
   switch (getNodeType()) {
     case kElementNode: {
       const Element& element = toElement(*this);
 
+      // 1. If its namespace is not null and its namespace prefix is prefix,
+      // then return namespace.
       if (!element.namespaceURI().isNull() && element.prefix() == prefix)
         return element.namespaceURI();
 
+      // 2. If it has an attribute whose namespace is the XMLNS namespace,
+      // namespace prefix is "xmlns", and local name is prefix, or if prefix is
+      // null and it has an attribute whose namespace is the XMLNS namespace,
+      // namespace prefix is null, and local name is "xmlns", then return its
+      // value if it is not the empty string, and null otherwise.
       AttributeCollection attributes = element.attributes();
       for (const Attribute& attr : attributes) {
         if (attr.prefix() == xmlnsAtom && attr.localName() == prefix) {
           if (!attr.value().isEmpty())
             return attr.value();
           return nullAtom;
         }
         if (attr.localName() == xmlnsAtom && prefix.isNull()) {
           if (!attr.value().isEmpty())
             return attr.value();
           return nullAtom;
         }
       }
 
+      // 3. If its parent element is null, then return null.
+      // 4. Return the result of running locate a namespace on its parent
+      // element using prefix.
       if (Element* parent = parentElement())
         return parent->lookupNamespaceURI(prefix);
       return nullAtom;
     }
     case kDocumentNode:
       if (Element* de = toDocument(this)->documentElement())
         return de->lookupNamespaceURI(prefix);
       return nullAtom;
     case kDocumentTypeNode:
     case kDocumentFragmentNode:
@@ skipping 1286 matching lines @@
   if (node) {
     std::stringstream stream;
     node->printNodePathTo(stream);
     LOG(INFO) << stream.str();
   } else {
     LOG(INFO) << "Cannot showNodePath for <null>";
   }
 }
 
 #endif