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

Source/core/html/HTMLImageLoader.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2010 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
@@ skipping 26 matching lines @@
 {
 }
 
 HTMLImageLoader::~HTMLImageLoader()
 {
 }
 
 void HTMLImageLoader::dispatchLoadEvent()
 {
     // HTMLVideoElement uses this class to load the poster image, but it should not fire events for loading or failure.
-    if (element()->hasTagName(HTMLNames::videoTag))
+    if (isHTMLVideoElement(*element()))
         return;
 
     bool errorOccurred = image()->errorOccurred();
     if (!errorOccurred && image()->response().httpStatusCode() >= 400)
-        errorOccurred = element()->hasTagName(HTMLNames::objectTag); // An <object> considers a 404 to be an error and should fire onerror.
+        errorOccurred = isHTMLObjectElement(*element()); // An <object> considers a 404 to be an error and should fire onerror.
     element()->dispatchEvent(Event::create(errorOccurred ? EventTypeNames::error : EventTypeNames::load));
 }
 
 String HTMLImageLoader::sourceURI(const AtomicString& attr) const
 {
     return stripLeadingAndTrailingHTMLSpaces(attr);
 }
 
 void HTMLImageLoader::notifyFinished(Resource*)
 {
     ImageResource* cachedImage = image();
 
     RefPtr<Element> element = this->element();
     ImageLoader::notifyFinished(cachedImage);
 
     bool loadError = cachedImage->errorOccurred() || cachedImage->response().httpStatusCode() >= 400;
 
-    if (loadError && element->hasTagName(HTMLNames::objectTag))
+    if (loadError && isHTMLObjectElement(*element))
         toHTMLObjectElement(element)->renderFallbackContent();
 }
 
 }