Separate the NTP app ordering from the app list app ordering

chrome/browser/extensions/extension_ordering.h

Index: chrome/browser/extensions/extension_ordering.h
diff --git a/chrome/browser/extensions/extension_ordering.h b/chrome/browser/extensions/extension_ordering.h
new file mode 100644
index 0000000000000000000000000000000000000000..7c267f2670d9c68205db305c92fd7d0b32886c78
--- /dev/null
+++ b/chrome/browser/extensions/extension_ordering.h
@@ -0,0 +1,66 @@
+// Copyright (c) 2013 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.
+
+#ifndef CHROME_BROWSER_EXTENSIONS_EXTENSION_ORDERING_H_
+#define CHROME_BROWSER_EXTENSIONS_EXTENSION_ORDERING_H_
+
+#include <string>
+
+#include "chrome/common/extensions/extension.h"
+
+class ExtensionScopedPrefs;
+class ExtensionServiceInterface;
+class PrefService;
+
+// An synced ordering of apps located in extension prefs.
+class ExtensionOrdering {
+ public:
+  explicit ExtensionOrdering(ExtensionScopedPrefs* extension_scoped_prefs);
+  ~ExtensionOrdering();
+
+  // Set the ExtensionService to syncs order changes.
+  void SetExtensionService(ExtensionServiceInterface* extension_service);
+
+  // Properly initialize ExtensionOrdering internal values that require
+  // |extension_ids|.
+  virtual void Initialize(const extensions::ExtensionIdList& extension_ids) = 0;
+
+  // Resolves any conflicts that might be created as a result of syncing that
+  // results in two extensions having the same position in the ordering. After
+  // this is called, it is guaranteed that there will be no collisions.
+  virtual void FixSyncCollisions() = 0;
+
+  // Add an extension so that it precedes all other extensions in the ordering.
+  virtual void InsertAtFront(const std::string& extension_id) = 0;
+
+  // Add an extension so that all other extensions precede it in the ordering.
+  virtual void InsertAtBack(const std::string& extension_id) = 0;
+
+  // Add to the next available position as determined by the implementation of
+  // this ordering.
+  virtual void InsertAtNextAvailable(const std::string& extension_id) = 0;
+
+  // Updates the moved extension in the ordering so that it is now located after
+  // the given predecessor and before the successor. Empty strings are used to
+  // indicate no successor or predecessor.
+  virtual void OnExtensionMoved(const std::string& moved_extension_id,
+                                const std::string& predecessor_extension_id,
+                                const std::string& successor_extension_id) = 0;
+
+  // Removes an app from the ordering.
+  virtual void Erase(const std::string& extension_id) = 0;
+
+  // Returns true if |extension1| appears before |extension2| in the ordering.
+  virtual bool ExtensionPrecedes(const std::string& extension1,
+                                 const std::string& extension2) = 0;
+ protected:
+  // Syncs the extension if needed. It is an error to call this if the
+  // extension is not an application.
+  void SyncIfNeeded(const std::string& extension_id);
+
+  ExtensionScopedPrefs* extension_scoped_prefs_;  // Weak, owns this instance.
+  ExtensionServiceInterface* extension_service_;  // Weak.
+};
+
+#endif  // CHROME_BROWSER_EXTENSIONS_EXTENSION_ORDERING_H_