Devirtualize Document class type checking

Source/core/dom/Document.cpp

Index: Source/core/dom/Document.cpp
diff --git a/Source/core/dom/Document.cpp b/Source/core/dom/Document.cpp
index 27635b695dc58bf71f21d64297d0f9b3a16f5bad..de8c587093caff46d1b4d15bdd043fb7dc01b21d 100644
--- a/Source/core/dom/Document.cpp
+++ b/Source/core/dom/Document.cpp
@@ -373,7 +373,7 @@ static void printNavigationErrorMessage(Frame* frame, const KURL& activeURL, con
 
 uint64_t Document::s_globalTreeVersion = 0;
 
-Document::Document(Frame* frame, const KURL& url, bool isXHTML, bool isHTML)
+Document::Document(Frame* frame, const KURL& url, unsigned documentClass)
     : ContainerNode(0, CreateDocument)
     , TreeScope(this)
     , m_styleResolverThrowawayTimer(this, &Document::styleResolverThrowawayTimerFired)
@@ -408,8 +408,7 @@ Document::Document(Frame* frame, const KURL& url, bool isXHTML, bool isHTML)
     , m_createRenderers(true)
     , m_accessKeyMapValid(false)
     , m_useSecureKeyboardEntryWhenActive(false)
-    , m_isXHTML(isXHTML)
-    , m_isHTML(isHTML)
+    , m_documentClass(documentClass)
     , m_isViewSource(false)
     , m_sawElementsInKnownNamespaces(false)
     , m_isSrcdocDocument(false)
@@ -760,7 +759,7 @@ PassRefPtr<Element> Document::createElement(const AtomicString& name, ExceptionC
         return 0;
     }
 
-    if (m_isXHTML)
+    if (isXHTMLDocument())
         return HTMLElementFactory::createHTMLElement(QualifiedName(nullAtom, name, xhtmlNamespaceURI), this, 0, false);
 
     return createElement(QualifiedName(nullAtom, name, nullAtom), false);