In Bookmark manager 'Add page' and 'Add Folder' always add new page or folder at the end.

chrome/browser/resources/bookmark_manager/js/main.js

 // Copyright (c) 2012 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.
 
 (function() {
 /** @const */ var BookmarkList = bmm.BookmarkList;
 /** @const */ var BookmarkTree = bmm.BookmarkTree;
 /** @const */ var Command = cr.ui.Command;
 /** @const */ var LinkKind = cr.LinkKind;
 /** @const */ var ListItem = cr.ui.ListItem;
@@ skipping 1011 matching lines @@
 
 /**
  * Callback for the new folder command. This creates a new folder and starts
  * a rename of it.
  * @param {EventTarget=} opt_target The target to create a new folder in.
  */
 function newFolder(opt_target) {
   performGlobalUndo = null;  // This can't be undone, so disable global undo.
 
   var parentId = computeParentFolderForNewItem();
-
+  var selectedItem = bmm.list.selectedItem;
+  var newIndex;
   // Callback is called after tree and list data model updated.
   function createFolder(callback) {
+    if (selectedItem && document.activeElement != bmm.tree &&
+        !bmm.isFolder(selectedItem)) {
+      newIndex = bmm.list.dataModel.indexOf(selectedItem) + 1;
+    }
     chrome.bookmarks.create({
       title: loadTimeData.getString('new_folder_name'),
-      parentId: parentId
+      parentId: parentId,
+      index: newIndex
     }, callback);
   }
 
   if ((opt_target || document.activeElement) == bmm.tree) {
     createFolder(function(newNode) {
       navigateTo(newNode.id, function() {
         bmm.treeLookup[newNode.id].editing = true;
       });
     });
     return;
   }
 
   function editNewFolderInList() {
     createFolder(function() {
       var index = bmm.list.dataModel.length - 1;
+      if (newIndex != undefined)
+        index = newIndex;

[xiyuan, 2015/01/07 17:14:03]

As Bernhard pointed out, |newIndex| does not necessary points at the correct
item here. One possible case is when this callback happened after bookmark sync
kicks in and brings in extra bookmarks in dataModel before the newly created
item.

We probably should use the index in the BookmarkTreeNode passed in
chrome.bookmarks.create callback instead of |newIndex|. See
"createFolder(function(newNode) {" at line 1048 of this patch.

[Deepak, 2015/01/08 13:41:13]

@xiyuan
Actually the code for bmm.tree and the bmm.list case is separate.
editNewFolderInList() does not get called for bmm.tree case.
and 
'if ((opt_target || document.activeElement) == bmm.tree)'
get executed in bmm.tree case only.
This patch is for bmm.list case.
I agree with you & Bernhard that I should not use newIndex here, As its value
can be changed. So I am using the index that is present in the callback, as
callback comes with the newly added node.
I am making changes and uploading again.
PTAL.

       var sm = bmm.list.selectionModel;
       sm.anchorIndex = sm.leadIndex = sm.selectedIndex = index;
       scrollIntoViewAndMakeEditable(index);
     });
   }
 
   navigateTo(parentId, editNewFolderInList);
 }
 
 /**
@@ skipping 10 matching lines @@
       item.editing = true;
   }, 0);
 }
 
 /**
  * Adds a page to the current folder. This is called by the
  * add-new-bookmark-command handler.
  */
 function addPage() {
   var parentId = computeParentFolderForNewItem();
+  var selectedItem = bmm.list.selectedItem;
+  var newIndex;
+  function editNewBookmark() {
+    if (selectedItem && document.activeElement != bmm.tree &&
+        !bmm.isFolder(selectedItem)) {
+      newIndex = bmm.list.dataModel.indexOf(selectedItem) + 1;
+    }
 
-  function editNewBookmark() {
     var fakeNode = {
       title: '',
       url: '',
       parentId: parentId,
+      index: newIndex,
       id: 'new'
     };
     var dataModel = bmm.list.dataModel;
-    var length = dataModel.length;
-    dataModel.splice(length, 0, fakeNode);
+    var index = dataModel.length;
+    if (newIndex != undefined)
+      index = newIndex;
+    dataModel.splice(index, 0, fakeNode);
     var sm = bmm.list.selectionModel;
-    sm.anchorIndex = sm.leadIndex = sm.selectedIndex = length;
-    scrollIntoViewAndMakeEditable(length);
+    sm.anchorIndex = sm.leadIndex = sm.selectedIndex = index;
+    scrollIntoViewAndMakeEditable(index);
   };
 
   navigateTo(parentId, editNewBookmark);
 }
 
 /**
  * This function is used to select items after a user action such as paste, drop
  * add page etc.
  * @param {BookmarkList|BookmarkTree} target The target of the user action.
  * @param {string=} opt_selectedTreeId If provided, then select that tree id.
@@ skipping 384 matching lines @@
 
   cr.ui.FocusOutlineManager.forDocument(document);
   initializeSplitter();
   bmm.addBookmarkModelListeners();
   dnd.init(selectItemsAfterUserAction);
   bmm.tree.reload();
 }
 
 initializeBookmarkManager();
 })();