Use new is*Element() helper functions more in editing code

Source/core/editing/TextIterator.cpp

Index: Source/core/editing/TextIterator.cpp
diff --git a/Source/core/editing/TextIterator.cpp b/Source/core/editing/TextIterator.cpp
index a0e041e37711a138cb41304f1836e854b95ce80b..3c452ce0bcb46bf8bd74f4379d47a8edb93838d9 100644
--- a/Source/core/editing/TextIterator.cpp
+++ b/Source/core/editing/TextIterator.cpp
@@ -406,9 +406,9 @@ void TextIterator::advance()
                 } else if (renderer && (renderer->isImage() || renderer->isWidget()
                     || (m_node && m_node->isElementNode()
                     && (toElement(m_node)->isFormControlElement()
-                    || toElement(m_node)->hasTagName(legendTag)
-                    || toElement(m_node)->hasTagName(meterTag)
-                    || toElement(m_node)->hasTagName(progressTag))))) {
+                    || isHTMLLegendElement(toElement(*m_node))
+                    || isHTMLMeterElement(toElement(*m_node))
+                    || isHTMLProgressElement(toElement(*m_node)))))) {
                     handledNode = handleReplacedElement();
                 } else {
                     handledNode = handleNonTextNode();
@@ -808,9 +808,9 @@ static bool shouldEmitNewlineForNode(Node* node, bool emitsOriginalText)
 {
     RenderObject* renderer = node->renderer();
 
-    if (renderer ? !renderer->isBR() : !node->hasTagName(brTag))
+    if (renderer ? !renderer->isBR() : !isHTMLBRElement(node))
         return false;
-    return emitsOriginalText || !(node->isInShadowTree() && node->shadowHost()->hasTagName(inputTag));
+    return emitsOriginalText || !(node->isInShadowTree() && isHTMLInputElement(*node->shadowHost()));
 }
 
 static bool shouldEmitNewlinesBeforeAndAfterNode(Node& node)
@@ -975,7 +975,7 @@ bool TextIterator::shouldRepresentNodeOffsetZero()
     // Additionally, if the range we are iterating over contains huge sections of unrendered content,
     // we would create VisiblePositions on every call to this function without this check.
     if (!m_node->renderer() || m_node->renderer()->style()->visibility() != VISIBLE
-        || (m_node->renderer()->isRenderBlockFlow() && !toRenderBlock(m_node->renderer())->height() && !m_node->hasTagName(bodyTag)))
+        || (m_node->renderer()->isRenderBlockFlow() && !toRenderBlock(m_node->renderer())->height() && !isHTMLBodyElement(*m_node)))
         return false;
 
     // The startPos.isNotNull() check is needed because the start could be before the body,