Change bookmarkManager API from experimental to private.

chrome/browser/resources/bookmark_manager/js/bmm/bookmark_tree.js

 // Copyright (c) 2011 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.
 
 
 cr.define('bmm', function() {
   const Tree = cr.ui.Tree;
   const TreeItem = cr.ui.TreeItem;
 
   var treeLookup = {};
@@ skipping 247 matching lines @@
             var item = new BookmarkTreeItem(bookmarkNode);
             parentTreeItem.add(item);
             var anyChildren = buildTreeItems(item, bookmarkNode.children);
             item.expanded = anyChildren && expandedManager.get(bookmarkNode.id);
           }
         }
         return hasDirectories;
       }
 
       var self = this;
-      chrome.experimental.bookmarkManager.getSubtree('', true, function(root) {
+      chrome.bookmarkManagerPrivate.getSubtree('', true, function(root) {
         self.clear();
         buildTreeItems(self, root[0].children);
         cr.dispatchSimpleEvent(self, 'load');
       });
     },
 
     /**
      * Clears the tree.
      */
     clear: function() {
@@ skipping 20 matching lines @@
     }
   };
 
   return {
     BookmarkTree: BookmarkTree,
     BookmarkTreeItem: BookmarkTreeItem,
     treeLookup: treeLookup,
     tree: tree
   };
 });