Core: Move form method into its own module

Ref #9647

tests/unit/core/core.js

@@ -1,7 +1,8 @@
 define( [
 	"jquery",
 	"lib/common",
-	"ui/core"
+	"ui/core",
+	"ui/form"
 ], function( $, common ) {
 
 module( "core - jQuery extensions" );

ui/core.js

@@ -24,6 +24,7 @@
 			"./disable-selection",
 			"./escape-selector",
 			"./focusable",
+			"./form",
 			"./version"
 		], factory );
 	} else {
@@ -131,13 +132,6 @@ $.fn.extend( {
 		} );
 	},
 
-	// Support: IE8 Only
-	// IE8 does not support the form attribute and when it is supplied. It overwrites the form prop
-	// with a string, so we need to find the proper form.
-	form: function() {
-		return typeof this[ 0 ].form === "string" ? this.closest( "form" ) : $( this[ 0 ].form );
-	},
-
 	labels: function() {
 		var ancestor, selector, id, labels, ancestors;
 

ui/form-reset-mixin.js

@@ -4,7 +4,7 @@
 		// AMD. Register as an anonymous module.
 		define( [
 			"jquery",
-			"ui/core",
+			"./form",
 			"./version"
 		], factory );
 	} else {

ui/form.js

@@ -0,0 +1,20 @@
+( function( factory ) {
+	if ( typeof define === "function" && define.amd ) {
+
+		// AMD. Register as an anonymous module.
+		define( [ "jquery", "./version" ], factory );
+	} else {
+
+		// Browser globals
+		factory( jQuery );
+	}
+} ( function( $ ) {
+
+// Support: IE8 Only
+// IE8 does not support the form attribute and when it is supplied. It overwrites the form prop
+// with a string, so we need to find the proper form.
+return $.fn.form = function() {
+	return typeof this[ 0 ].form === "string" ? this.closest( "form" ) : $( this[ 0 ].form );
+};
+
+} ) );