cros: Allow default app order to be loaded from an external file.

chrome/browser/chromeos/extensions/default_app_order.h

Index: chrome/browser/chromeos/extensions/default_app_order.h
diff --git a/chrome/browser/chromeos/extensions/default_app_order.h b/chrome/browser/chromeos/extensions/default_app_order.h
new file mode 100644
index 0000000000000000000000000000000000000000..fc1324c4f6da9035a746cc9b778802a2238d0dd9
--- /dev/null
+++ b/chrome/browser/chromeos/extensions/default_app_order.h
@@ -0,0 +1,48 @@
+// 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.
+
+#ifndef CHROME_BROWSER_CHROMEOS_EXTENSIONS_DEFAULT_APP_ORDER_H_
+#define CHROME_BROWSER_CHROMEOS_EXTENSIONS_DEFAULT_APP_ORDER_H_
+
+#include <string>
+#include <vector>
+
+#include "base/basictypes.h"
+#include "base/synchronization/waitable_event.h"
+
+namespace chromeos {
+namespace default_app_order {
+
+// ExternalLoader checks FILE_DEFAULT_APP_ORDER and loads it if the file
+// exists. Otherwise, it uses the default built-in order. The file loading runs
+// asynchronously on start up except for the browser restart path, in which
+// case, start up will wait for the file check to finish because user profile
+// might need to access the ordinals data.
+class ExternalLoader {
+ public:
+  // Constructs an ExternalLoader and starts file loading. |async| is true to
+  // load the file asynchronously on the blocking pool.
+  explicit ExternalLoader(bool async);
+  ~ExternalLoader();
+
+  const std::vector<std::string>& GetAppIds();
+
+ private:
+  void Load();
+
+  // A vector of app id strings that defines the default order of apps.
+  std::vector<std::string> app_ids_;
+
+  base::WaitableEvent loaded_;
+
+  DISALLOW_COPY_AND_ASSIGN(ExternalLoader);
+};
+
+// Gets the ordered list of app ids.
+void Get(std::vector<std::string>* app_ids);
+
+}  // namespace default_app_order
+}  // namespace chromeos
+
+#endif  // CHROME_BROWSER_CHROMEOS_EXTENSIONS_DEFAULT_APP_ORDER_H_