[MD Bookmarks] Flatten sidebar.

chrome/browser/resources/md_bookmarks/util.js

Index: chrome/browser/resources/md_bookmarks/util.js
diff --git a/chrome/browser/resources/md_bookmarks/util.js b/chrome/browser/resources/md_bookmarks/util.js
index 9c1e942146e8e072d41d79e71f22a249c8983f79..02090175ca79b9446817cfa28e037ea4948d6836 100644
--- a/chrome/browser/resources/md_bookmarks/util.js
+++ b/chrome/browser/resources/md_bookmarks/util.js
@@ -48,12 +48,52 @@ cr.define('bookmarks.util', function() {
     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,
@@ -64,12 +104,18 @@ cr.define('bookmarks.util', function() {
         anchor: null,
         count: 0,
       },
+      sidebar: {
+        folders: [],
+        folderMap: {},
+      },
     };
   }
 
   return {
     createEmptyState: createEmptyState,
+    createFolderMap: createFolderMap,
     getDisplayedList: getDisplayedList,
+    initializeSidebar: initializeSidebar,
     normalizeNodes: normalizeNodes,
   };
 });