Correction in docScroll (#360)

Variable "node" leverages doc given by window instead of the one given as a parameter. Noticed when putting a popup into an iframe where the content of the iframe has quite some height.
(cherry picked from commit 88c915f)

dom-geometry.js

@@ -425,7 +425,7 @@ define(["./sniff", "./_base/window","./dom", "./dom-style"],
 		// returns: Object
 
 		doc = doc || win.doc;
-		var node = win.doc.parentWindow || win.doc.defaultView;   // use UI window, not dojo.global window.   TODO: use dojo/window::get() except for circular dependency problem
+		var node = doc.parentWindow || doc.defaultView;   // use UI window, not dojo.global window.   TODO: use dojo/window::get() except for circular dependency problem
 		return "pageXOffset" in node ? {x: node.pageXOffset, y: node.pageYOffset } :
 			(node = has("quirks") ? win.body(doc) : doc.documentElement) &&
 				{x: geom.fixIeBiDiScrollLeft(node.scrollLeft || 0, doc), y: node.scrollTop || 0 };