Introduce FastShowPickler which will be used for app list cold start.

chrome/browser/ui/app_list/fast_show_pickler.h

Index: chrome/browser/ui/app_list/fast_show_pickler.h
diff --git a/chrome/browser/ui/app_list/fast_show_pickler.h b/chrome/browser/ui/app_list/fast_show_pickler.h
new file mode 100644
index 0000000000000000000000000000000000000000..26995304b00b48fa1f9b54bfabaa6f23a5d81cf6
--- /dev/null
+++ b/chrome/browser/ui/app_list/fast_show_pickler.h
@@ -0,0 +1,41 @@
+// Copyright 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_UI_APP_LIST_FAST_SHOW_PICKLER_H_
+#define CHROME_BROWSER_UI_APP_LIST_FAST_SHOW_PICKLER_H_
+
+#include <string>
+
+#include "base/memory/scoped_ptr.h"
+#include "base/pickle.h"
+#include "base/strings/string16.h"
+#include "ui/app_list/app_list_item_model.h"
+#include "ui/app_list/app_list_model.h"
+
+
+// Functions for pickling/unpickling AppListModel for fast show. Fast show is
+// where the app list is put on the screen using data retrieved from a cache
+// before the extension system has loaded.
+class FastShowPickler {
+ public:
+  // The version that this pickler understands.
+  static const int kVersion;
+
+  // Pickles a subset of the data in |model| that is useful for doing a fast
+  // show of the app list.
+  static scoped_ptr<Pickle> PickleAppListModelForFastShow(
+      app_list::AppListModel* model);
+
+  // Given a Pickle created by PickleAppListModelForFastShow(), this creates an
+  // AppListModel that represents it.
+  static scoped_ptr<app_list::AppListModel> UnpickleAppListModelForFastShow(
+      Pickle* pickle);
+
+  // Copies parts that are needed to show the app list quickly on startup from
+  // |src| to |dest|.
+  static void CopyOver(
+      app_list::AppListModel* src, app_list::AppListModel* dest);
+};
+
+#endif  // CHROME_BROWSER_UI_APP_LIST_FAST_SHOW_PICKLER_H_