Add private system extension API to get system update status

chrome/browser/extensions/system/system_api.h

 // Copyright (c) 2011 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.
 
 // This extension API contains system-wide preferences and functions that shall
 // be only available to component extensions.
 
 #ifndef CHROME_BROWSER_EXTENSIONS_SYSTEM_SYSTEM_API_H_
 #define CHROME_BROWSER_EXTENSIONS_SYSTEM_SYSTEM_API_H_
 
-#include "chrome/browser/extensions/extension_preference_api.h"
-
-#include <string>
-
-namespace base {
-class Value;
-}
+#include "chrome/browser/extensions/extension_function.h"
 
 namespace extensions {
 
 class GetIncognitoModeAvailabilityFunction : public SyncExtensionFunction {
  public:
-  virtual ~GetIncognitoModeAvailabilityFunction();
+  virtual ~GetIncognitoModeAvailabilityFunction() {}
   virtual bool RunImpl() OVERRIDE;
   DECLARE_EXTENSION_FUNCTION_NAME("systemPrivate.getIncognitoModeAvailability")
 };
 
+// API function which returns the status of system update.
+class GetUpdateStatusFunction : public SyncExtensionFunction {
+ public:
+  virtual ~GetUpdateStatusFunction() {}
+  virtual bool RunImpl() OVERRIDE;
+  DECLARE_EXTENSION_FUNCTION_NAME("systemPrivate.getUpdateStatus")
+};
+
 }  // namespace extensions
 
 #endif  // CHROME_BROWSER_EXTENSIONS_SYSTEM_SYSTEM_API_H_