DevTools: Reduce code via using document.createElementWithClass and document.createChild.

Source/devtools/front_end/common/DOMExtension.js

 /*
  * Copyright (C) 2007 Apple Inc.  All rights reserved.
  * 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:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
@@ skipping 421 matching lines @@
 {
     return this.totalOffset().left;
 }
 
 /**
  * @return {number}
  */
 Element.prototype.totalOffsetTop = function()
 {
     return this.totalOffset().top;
-
 }
 
 /**
  * @return {!{left: number, top: number}}
  */
 Element.prototype.totalOffset = function()
 {
     var rect = this.getBoundingClientRect();
     return { left: rect.left, top: rect.top };
 }
@@ skipping 291 matching lines @@
  */
 function isEnterKey(event) {
     // Check if in IME.
     return event.keyCode !== 229 && event.keyIdentifier === "Enter";
 }
 
 function consumeEvent(e)
 {
     e.consume();
 }