[Fixed Position] Add element factory

Add element factory, which will take on responsibility
for populating initial states of elements and (if necessary)
prompting for user input. WTD-880.

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

@@ -0,0 +1,48 @@
+/*global define*/
+
+define(
+    [],
+    function () {
+        "use strict";
+
+        var INITIAL_STATES = {
+                "fixed.image": {
+                    url: "http://www.nasa.gov/sites/default/themes/NASAPortal/images/nasa-logo.gif"
+                }
+            },
+            DIALOGS = {
+
+            };
+
+        /**
+         * The ElementFactory creates new instances of elements for the
+         * fixed position view, prompting for user input where necessary.
+         * @param {DialogService} dialogService service to request user input
+         * @constructor
+         */
+        function ElementFactory(dialogService) {
+            return {
+                /**
+                 * Create a new element for the fixed position view.
+                 * @param {string} type the type of element to create
+                 * @returns {Promise|object} the created element, or a promise
+                 *          for that element
+                 */
+                createElement: function (type) {
+                    var initialState = INITIAL_STATES[type] || {};
+
+                    // Clone that state
+                    initialState = JSON.parse(JSON.stringify(initialState));
+
+                    // Show a dialog to configure initial state, if appropriate
+                    return DIALOGS[type] ? dialogService.getUserInput(
+                        DIALOGS[type],
+                        initialState
+                    ) : initialState;
+                }
+            };
+        }
+
+        return ElementFactory;
+    }
+);