[Edit] Refresh Library less aggressively

Update the root object (used to populate the Library pane)
less often, to avoid recreating the whole tree and thereby
causing the tree to collapse. WTD-788.

platform/commonUI/edit/bundle.json

@@ -16,6 +16,11 @@
                 "key": "EditActionController",
                 "implementation": "EditActionController.js",
                 "depends": [ "$scope" ]
+            },
+            {
+                "key": "EditPanesController",
+                "implementation": "controllers/EditPanesController.js",
+                "depends": [ "$scope" ]
             }
         ],
         "actions": [
@@ -72,7 +77,7 @@
             {
                 "key": "edit-object",
                 "templateUrl": "templates/edit-object.html",
-                "uses": [ "view", "context" ]
+                "uses": [ "view" ]
             },
             {
                 "key": "edit-action-buttons",

platform/commonUI/edit/res/templates/edit-object.html

@@ -18,10 +18,13 @@
         </div>
         <div class="splitter"></div>
         <div class='abs pane right edit-objects menus-to-left'>
-            <div class='holder abs split-layout horizontal'>
+            <div class='holder abs split-layout horizontal'
+                 ng-controller='EditPanesController as editPanes'>
 	            <div class="abs pane top accordion" ng-controller="ToggleController as toggle">
                 <mct-container key="accordion" title="Library">
-                    <mct-representation key="'tree'" alias="foo1" mct-object="context.getRoot()">
+                    <mct-representation key="'tree'"
+                                        alias="foo1"
+                                        mct-object="editPanes.getRoot()">
                     </mct-representation>
                 </mct-container>
 		        </div>

platform/commonUI/edit/src/controllers/EditPanesController.js

@@ -0,0 +1,47 @@
+/*global define*/
+
+define(
+    [],
+    function () {
+        "use strict";
+
+        /**
+         * Supports the Library and Elements panes in Edit mode.
+         * @constructor
+         */
+        function EditPanesController($scope) {
+            var root;
+
+            // Update root object based on represented object
+            function updateRoot(domainObject) {
+                var context = domainObject &&
+                    domainObject.getCapability('context'),
+                    newRoot = context && context.getRoot(),
+                    oldId = root && root.getId(),
+                    newId = newRoot && newRoot.getId();
+
+                // Only update if this has actually changed,
+                // to avoid excessive refreshing.
+                if (oldId !== newId) {
+                    root = newRoot;
+                }
+            }
+
+            // Update root when represented object changes
+            $scope.$watch('domainObject', updateRoot);
+
+            return {
+                /**
+                 * Get the root-level domain object, as reported by the
+                 * represented domain object.
+                 * @returns {DomainObject} the root object
+                 */
+                getRoot: function () {
+                    return root;
+                }
+            };
+        }
+
+        return EditPanesController;
+    }
+);