Introduce isHTMLTableElement and toHTMLTableElement

Source/core/html/parser/HTMLTreeBuilder.cpp

Index: Source/core/html/parser/HTMLTreeBuilder.cpp
diff --git a/Source/core/html/parser/HTMLTreeBuilder.cpp b/Source/core/html/parser/HTMLTreeBuilder.cpp
index 48f511cd276efdc40951896183fba287e9edccf4..ee860f1a0ffcd542e7a45daf48051fce68e0337f 100644
--- a/Source/core/html/parser/HTMLTreeBuilder.cpp
+++ b/Source/core/html/parser/HTMLTreeBuilder.cpp
@@ -36,6 +36,7 @@
 #include "core/dom/DocumentFragment.h"
 #include "core/html/HTMLFormElement.h"
 #include "core/html/HTMLOptGroupElement.h"
+#include "core/html/HTMLTableElement.h"
 #include "core/html/parser/AtomicHTMLToken.h"
 #include "core/html/parser/HTMLDocumentParser.h"
 #include "core/html/parser/HTMLParserIdioms.h"
@@ -1620,7 +1621,7 @@ void HTMLTreeBuilder::resetInsertionModeAppropriately()
         if (item->hasTagName(colgroupTag)) {
             return setInsertionMode(InColumnGroupMode);
         }
-        if (item->hasTagName(tableTag))
+        if (isHTMLTableElement(item->node()))
             return setInsertionMode(InTableMode);
         if (item->hasTagName(headTag)) {
             if (!m_fragmentContext.fragment() || m_fragmentContext.contextElement() != item->node())
@@ -2330,7 +2331,7 @@ ReprocessBuffer:
         ASSERT(insertionMode() == InTableMode || insertionMode() == InTableBodyMode || insertionMode() == InRowMode);
         ASSERT(m_pendingTableCharacters.isEmpty());
         if (m_tree.currentStackItem()->isElementNode()
-            && (m_tree.currentStackItem()->hasTagName(HTMLNames::tableTag)
+            && (isHTMLTableElement(m_tree.currentStackItem()->node())
                 || m_tree.currentStackItem()->hasTagName(HTMLNames::tbodyTag)
                 || m_tree.currentStackItem()->hasTagName(HTMLNames::tfootTag)
                 || m_tree.currentStackItem()->hasTagName(HTMLNames::theadTag)