Prevent appearing INVALID position ordinal in sync.

chrome/browser/ui/app_list/chrome_app_list_item.cc

 // Copyright 2015 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.
 
 #include "chrome/browser/ui/app_list/chrome_app_list_item.h"
 
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/ui/app_list/app_list_service.h"
 #include "extensions/browser/app_sorting.h"
 #include "extensions/browser/extension_system.h"
@@ skipping 44 matching lines @@
   // An existing synced position exists, use that.
   set_position(sync_item->item_ordinal);
   // Only set the name from the sync item if it is empty.
   if (name().empty())
     SetName(sync_item->item_name);
 }
 
 void ChromeAppListItem::SetDefaultPositionIfApplicable() {
   syncer::StringOrdinal page_ordinal;
   syncer::StringOrdinal launch_ordinal;
-  if (GetAppSorting()->GetDefaultOrdinals(id(), &page_ordinal,
-                                          &launch_ordinal) &&
-      page_ordinal.IsValid() && launch_ordinal.IsValid()) {
-    set_position(syncer::StringOrdinal(page_ordinal.ToInternalValue() +
-                                       launch_ordinal.ToInternalValue()));
+  extensions::AppSorting* app_sorting = GetAppSorting();
+  if (!app_sorting->GetDefaultOrdinals(id(), &page_ordinal,
+                                       &launch_ordinal) ||
+      !page_ordinal.IsValid() || !launch_ordinal.IsValid()) {
+    app_sorting->EnsureValidOrdinals(id(), syncer::StringOrdinal());
+    page_ordinal = app_sorting->GetPageOrdinal(id());
+    launch_ordinal = app_sorting->GetAppLaunchOrdinal(id());
   }
+  DCHECK(page_ordinal.IsValid());
+  DCHECK(launch_ordinal.IsValid());
+  set_position(syncer::StringOrdinal(page_ordinal.ToInternalValue() +
+                                     launch_ordinal.ToInternalValue()));
 }