Core: Remove .zIndex()

Fixes #9156

Author: scottgonzalez

build/tasks/testswarm.js

@@ -15,7 +15,6 @@ var versions = {
 		"Autocomplete": "autocomplete/autocomplete.html",
 		"Button": "button/button.html",
 		"Core": "core/core.html",
-		"Core_deprecated": "core/core_deprecated.html",
 		"Datepicker": "datepicker/datepicker.html",
 		"Dialog": "dialog/dialog.html",
 		"Draggable": "draggable/draggable.html",

tests/unit/all.html

@@ -20,7 +20,6 @@
 			"autocomplete/autocomplete.html",
 			"button/button.html",
 			"core/core.html",
-			"core/core_deprecated.html",
 			"datepicker/datepicker.html",
 			"dialog/dialog.html",
 			"draggable/draggable.html",

tests/unit/core/core_deprecated.html

@@ -223,35 +223,6 @@ $.fn.extend({
 
 	enableSelection: function() {
 		return this.unbind( ".ui-disableSelection" );
-	},
-
-	zIndex: function( zIndex ) {
-		if ( zIndex !== undefined ) {
-			return this.css( "zIndex", zIndex );
-		}
-
-		if ( this.length ) {
-			var elem = $( this[ 0 ] ), position, value;
-			while ( elem.length && elem[ 0 ] !== document ) {
-				// Ignore z-index if position is set to a value where z-index is ignored by the browser
-				// This makes behavior of this function consistent across browsers
-				// WebKit always returns auto if the element is positioned
-				position = elem.css( "position" );
-				if ( position === "absolute" || position === "relative" || position === "fixed" ) {
-					// IE returns 0 when zIndex is not specified
-					// other browsers return a string
-					// we ignore the case of nested elements with an explicit value of 0
-					// <div style="z-index: -10;"><div style="z-index: 0;"></div></div>
-					value = parseInt( elem.css( "zIndex" ), 10 );
-					if ( !isNaN( value ) && value !== 0 ) {
-						return value;
-					}
-				}
-				elem = elem.parent();
-			}
-		}
-
-		return 0;
 	}
 });