Avoid calling hasAttribute() and then getAttribute() for performance

Source/core/inspector/DOMEditor.cpp

 /*
  * Copyright (C) 2012 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 157 matching lines @@
         : InspectorHistory::Action("SetAttribute")
         , m_element(element)
         , m_name(name)
         , m_value(value)
         , m_hadAttribute(false)
     {
     }
 
     virtual bool perform(ExceptionState& exceptionState) OVERRIDE
     {
-        m_hadAttribute = m_element->hasAttribute(m_name);
+        const AtomicString& value = m_element->getAttribute(m_name);
+        m_hadAttribute = !value.isNull();
         if (m_hadAttribute)
-            m_oldValue = m_element->getAttribute(m_name);
+            m_oldValue = value;
         return redo(exceptionState);
     }
 
     virtual bool undo(ExceptionState& exceptionState) OVERRIDE
     {
         if (m_hadAttribute)
             m_element->setAttribute(m_name, m_oldValue, exceptionState);
         else
             m_element->removeAttribute(m_name);
         return true;
@@ skipping 261 matching lines @@
 bool DOMEditor::replaceWholeText(Text* textNode, const String& text, ErrorString* errorString)
 {
     TrackExceptionState exceptionState;
     bool result = replaceWholeText(textNode, text, exceptionState);
     populateErrorString(exceptionState, errorString);
     return result;
 }
 
 } // namespace WebCore