[MD Bookmarks] Flatten sidebar.

chrome/browser/resources/md_bookmarks/util.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.
 
 /**
  * @fileoverview Utility functions for the Bookmarks page.
  */
 
 cr.define('bookmarks.util', function() {
   /**
@@ skipping 30 matching lines @@
           childIds.push(child.id);
           queue.push(child);
         });
         node.children = childIds;
       }
     }
 
     return nodeMap;
   }
 
+  function initializeSidebar(rootNodeId, nodes) {
+    var folders = [];
+
+    var calculateFoldersBelow = function(nodeId, depth) {
+      var node = nodes[nodeId];
+      if (!node.children)
+        return;
+
+      folders.push({
+        id: node.id,
+        depth: depth,
+        visible: true,
+        open: true,
+      });
+      node.children.forEach(function(childId) {
+        calculateFoldersBelow(childId, depth + 1);
+      });
+    };
+
+    calculateFoldersBelow(rootNodeId, -1);
+
+    // Remove the root node.
+    folders.shift();
+    return {
+      folders: folders,
+      folderMap: createFolderMap(folders),
+    };
+  }
+
+  /**
+   * @param {!Array<SidebarFolder>} folders
+   * @return {!Object<string, number>}
+   */
+  function createFolderMap(folders) {
+    var folderMap = {};
+    folders.forEach(function(folder, idx) {
+      folderMap[folder.id] = idx;
+    });
+    return folderMap;
+  };
+
   /** @return {BookmarksPageState} */
   function createEmptyState() {
     return {
       nodes: {},
       selectedFolder: '0',
-      closedFolders: {},
       search: {
         term: '',
         inProgress: false,
         results: [],
       },
       selection: {
         items: {},
         anchor: null,
         count: 0,
       },
+      sidebar: {
+        folders: [],
+        folderMap: {},
+      },
     };
   }
 
   return {
     createEmptyState: createEmptyState,
+    createFolderMap: createFolderMap,
     getDisplayedList: getDisplayedList,
+    initializeSidebar: initializeSidebar,
     normalizeNodes: normalizeNodes,
   };
 });