Moves isHidden to src/css.js and re-introduces its use. No ticket. Closes gh-876

src/css.js

@@ -43,6 +43,11 @@ function vendorPropName( style, name ) {
 	return origName;
 }
 
+function isHidden( elem, el ) {
+	elem = el || elem;
+	return jQuery.css( elem, "display" ) === "none" || !jQuery.contains( elem.ownerDocument.documentElement, elem );
+}
+
 function showHide( elements, show ) {
 	var elem, display,
 		values = [],
@@ -65,8 +70,7 @@ function showHide( elements, show ) {
 			// Set elements which have been overridden with display: none
 			// in a stylesheet to whatever the default browser style is
 			// for such an element
-			if ( (elem.style.display === "" && curCSS( elem, "display" ) === "none") ||
-				!jQuery.contains( elem.ownerDocument.documentElement, elem ) ) {
+			if ( elem.style.display === "" && isHidden( elem ) ) {
 				values[ index ] = jQuery._data( elem, "olddisplay", css_defaultDisplay(elem.nodeName) );
 			}
 		} else {

src/effects.js

@@ -437,11 +437,6 @@ Tween.propHooks.scrollTop = Tween.propHooks.scrollLeft = {
 	}
 };
 
-function isHidden( elem, el ) {
-	elem = el || elem;
-	return curCSS( elem, "display" ) === "none" || !jQuery.contains( elem.ownerDocument.documentElement, elem );
-}
-
 jQuery.each([ "toggle", "show", "hide" ], function( i, name ) {
 	var cssFn = jQuery.fn[ name ];
 	jQuery.fn[ name ] = function( speed, easing, callback ) {