MD Bookmarks: Support policies for disabling bookmark editing

chrome/test/data/webui/md_bookmarks/dnd_manager_test.js

 // Copyright 2017 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 suite('drag and drop', function() {
   var app;
   var list;
   var rootFolderNode;
   var store;
   var dndManager;
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                 createItem('12'),
                 createItem('13'),
                 createFolder('14', []),
                 createFolder('15', []),
               ]),
           createFolder('2', [])),
       selectedFolder: '1',
     });
     store.replaceSingleton();
 
+    draggedIds = null;
     chrome.bookmarkManagerPrivate.startDrag = function(nodes, isTouch) {
       draggedIds = nodes;
     };
 
     app = document.createElement('bookmarks-app');
     replaceBody(app);
     list = app.$$('bookmarks-list');
     rootFolderNode = app.$$('bookmarks-folder-node');
     dndManager = app.dndManager_;
     dndManager.disableTimeoutsForTesting();
@@ skipping 379 matching lines @@
     dispatchDragEvent('dragstart', dragElement);
     assertDeepEquals(['14'], normalizeSet(store.data.selection.items));
     dispatchDragEvent('dragend', dragElement);
 
     // Dragging a folder node deselects any selected items in the bookmark list.
     dragElement = getFolderNode('15');
     dispatchDragEvent('dragstart', dragElement);
     assertDeepEquals([], normalizeSet(store.data.selection.items));
     dispatchDragEvent('dragend', dragElement);
   });
+
+  test('cannot drag items when editing is disabled', function() {
+    store.data.prefs.canEdit = false;
+    store.notifyObservers();
+
+    var dragElement = getFolderNode('11');
+    dispatchDragEvent('dragstart', dragElement);
+    assertEquals(null, draggedIds);
+  });
+
+  test('cannot start dragging unmodifiable items', function() {
+    store.data.nodes['2'].unmodifiable = 'managed';
+    store.notifyObservers();
+
+    var dragElement = getFolderNode('1');
+    dispatchDragEvent('dragstart', dragElement);
+    assertEquals(null, draggedIds);
+
+    dragElement = getFolderNode('2');
+    dispatchDragEvent('dragstart', dragElement);
+    assertEquals(null, draggedIds);
+  });
+
+  test('cannot drag onto folders with unmodifiable children', function() {
+    store.data.nodes['2'].unmodifiable = 'managed';
+    store.notifyObservers();
+
+    var dragElement = getListItem('12');
+    dispatchDragEvent('dragstart', dragElement);
+
+    // Can't drag onto the unmodifiable node.
+    var dragTarget = getFolderNode('2');
+    dispatchDragEvent('dragover', dragTarget);
+    assertEquals(
+        DropPosition.NONE, dndManager.calculateValidDropPositions_(dragTarget));
+  });
 });