Use the correct case converter for |localName| and |tagName|

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

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  *           (C) 2006 Alexey Proskuryakov (ap@webkit.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2011, 2012 Apple Inc. All
  * rights reserved.
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved.
  * (http://www.torchmobile.com/)
  * Copyright (C) 2008, 2009, 2011, 2012 Google Inc. All rights reserved.
@@ skipping 677 matching lines @@
 
 Element* Document::rootScroller() const {
   return m_rootScrollerController->get();
 }
 
 bool Document::isInMainFrame() const {
   return frame() && frame()->isMainFrame();
 }
 
 AtomicString Document::convertLocalName(const AtomicString& name) {
-  return isHTMLDocument() ? name.lower() : name;
+  return isHTMLDocument() ? name.lowerASCII() : name;
 }
 
 // https://dom.spec.whatwg.org/#dom-document-createelement
 Element* Document::createElement(const AtomicString& name,
                                  ExceptionState& exceptionState) {
   if (!isValidName(name)) {
     exceptionState.throwDOMException(
         InvalidCharacterError,
         "The tag name provided ('" + name + "') is not a valid name.");
     return nullptr;
@@ skipping 5953 matching lines @@
 }
 
 void showLiveDocumentInstances() {
   WeakDocumentSet& set = liveDocumentSet();
   fprintf(stderr, "There are %u documents currently alive:\n", set.size());
   for (blink::Document* document : set)
     fprintf(stderr, "- Document %p URL: %s\n", document,
             document->url().getString().utf8().data());
 }
 #endif