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

Index: chrome/browser/resources/bookmark_manager/js/main.js
diff --git a/chrome/browser/resources/bookmark_manager/js/main.js b/chrome/browser/resources/bookmark_manager/js/main.js
index efab6e96b883df797ce046c817ccc8074953e969..c599f6003708c1a7eb65f5f62c95c70da48530d4 100644
--- a/chrome/browser/resources/bookmark_manager/js/main.js
+++ b/chrome/browser/resources/bookmark_manager/js/main.js
@@ -1029,12 +1029,18 @@ 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);
   }
 
@@ -1050,6 +1056,8 @@ function newFolder(opt_target) {
   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);
@@ -1080,20 +1088,29 @@ function scrollIntoViewAndMakeEditable(index) {
  */
 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;
+    }
+
     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);