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

Source/core/loader/FormSubmission.cpp

 /*
  * Copyright (C) 2010 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 197 matching lines @@
             isMultiPartForm = false;
         }
     }
     WTF::TextEncoding dataEncoding = isMailtoForm ? UTF8Encoding() : FormDataBuilder::encodingFromAcceptCharset(copiedAttributes.acceptCharset(), document.inputEncoding(), document.defaultCharset());
     RefPtrWillBeRawPtr<DOMFormData> domFormData = DOMFormData::create(dataEncoding.encodingForFormSubmission());
     Vector<pair<String, String> > formValues;
 
     bool containsPasswordData = false;
     for (unsigned i = 0; i < form->associatedElements().size(); ++i) {
         FormAssociatedElement* control = form->associatedElements()[i];
-        HTMLElement* element = toHTMLElement(control);
-        if (!element->isDisabledFormControl())
+        ASSERT(control);
+        HTMLElement& element = toHTMLElement(*control);
+        if (!element.isDisabledFormControl())
             control->appendFormData(*domFormData, isMultiPartForm);
-        if (element->hasTagName(inputTag)) {
-            HTMLInputElement* input = toHTMLInputElement(element);
-            if (input->isTextField())
-                formValues.append(pair<String, String>(input->name().string(), input->value()));
-            if (input->isPasswordField() && !input->value().isEmpty())
+        if (isHTMLInputElement(element)) {
+            HTMLInputElement& input = toHTMLInputElement(element);
+            if (input.isTextField())
+                formValues.append(pair<String, String>(input.name().string(), input.value()));
+            if (input.isPasswordField() && !input.value().isEmpty())
                 containsPasswordData = true;
         }
     }
 
     RefPtr<FormData> formData;
     String boundary;
 
     if (isMultiPartForm) {
         formData = domFormData->createMultiPartFormData(domFormData->encoding());
         boundary = formData->boundary().data();
@@ skipping 40 matching lines @@
             frameRequest.resourceRequest().setHTTPContentType(m_contentType);
         else
             frameRequest.resourceRequest().setHTTPContentType(m_contentType + "; boundary=" + m_boundary);
     }
 
     frameRequest.resourceRequest().setURL(requestURL());
     FrameLoader::addHTTPOriginIfNeeded(frameRequest.resourceRequest(), AtomicString(m_origin));
 }
 
 }