[Fixed Position] Rename accessor

Rename utility function used by fixed position elements
to be more accurate. WTD-879.

platform/features/layout/src/elements/AccessorMutator.js

@@ -0,0 +1,26 @@
+/*global define*/
+
+define(
+    [],
+    function () {
+        "use strict";
+
+        /**
+         * Utility function for creating getter-setter functions,
+         * since these are frequently useful for element proxies.
+         * @constructor
+         * @param {Object} object the object to get/set values upon
+         * @param {string} key the property to get/set
+         */
+        function AccessorMutator(object, key) {
+            return function (value) {
+                if (arguments.length > 0) {
+                    object[key] = value;
+                }
+                return object[key];
+            };
+        }
+
+        return AccessorMutator;
+    }
+);