[DevTools] Replace usages of document with custom functions.

Source/devtools/front_end/network/RequestHTMLView.js

Index: Source/devtools/front_end/network/RequestHTMLView.js
diff --git a/Source/devtools/front_end/network/RequestHTMLView.js b/Source/devtools/front_end/network/RequestHTMLView.js
index fdfd4dbccaaaa364aaa0214c43b920dd764fd3c2..2943891cf2c97a9ba0c585d0662c1794d644a414 100644
--- a/Source/devtools/front_end/network/RequestHTMLView.js
+++ b/Source/devtools/front_end/network/RequestHTMLView.js
@@ -57,7 +57,7 @@ WebInspector.RequestHTMLView.prototype = {
         // We need to create iframe again each time because contentDocument
         // is deleted when iframe is removed from its parent.
         this.element.removeChildren();
-        var iframe = document.createElement("iframe");
+        var iframe = createElement("iframe");
         iframe.setAttribute("sandbox", ""); // Forbid to run JavaScript and set unique origin.
         iframe.setAttribute("src", this._dataURL);
         this.element.appendChild(iframe);