[DevTools] Replace usages of document with custom functions.

Source/devtools/front_end/layers/LayerDetailsView.js

 /*
  * Copyright (C) 2013 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 163 matching lines @@
 
     /**
      * @param {!Array.<string>} compositingReasons
      */
     _updateCompositingReasons: function(compositingReasons)
     {
         if (!compositingReasons || !compositingReasons.length) {
             this._compositingReasonsCell.textContent = "n/a";
             return;
         }
-        var fragment = document.createDocumentFragment();
+        var fragment = createDocumentFragment();
         for (var i = 0; i < compositingReasons.length; ++i) {
             if (i)
                 fragment.createTextChild(",");
-            var span = document.createElement("span");
+            var span = createElement("span");
             span.title = WebInspector.LayerDetailsView.CompositingReasonDetail[compositingReasons[i]] || "";
             span.textContent = compositingReasons[i];
             fragment.appendChild(span);
         }
         this._compositingReasonsCell.removeChildren();
         this._compositingReasonsCell.appendChild(fragment);
     },
 
     __proto__: WebInspector.VBox.prototype
 }