[Extensions] Convert some ChromeSyncExtensionFunctions

chrome/browser/chromeos/extensions/file_manager/private_api_strings.h

 // 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.
 //
 // This file only provides getStrings() as the .cc file for it is big.
 
 #ifndef CHROME_BROWSER_CHROMEOS_EXTENSIONS_FILE_MANAGER_PRIVATE_API_STRINGS_H_
 #define CHROME_BROWSER_CHROMEOS_EXTENSIONS_FILE_MANAGER_PRIVATE_API_STRINGS_H_
 
 #include "chrome/browser/extensions/chrome_extension_function.h"
 
 namespace extensions {
 
 // Implements the chrome.fileManagerPrivate.getStrings method.
 // Used to get strings for the file manager from JavaScript.
-class FileManagerPrivateGetStringsFunction
-    : public ChromeSyncExtensionFunction {
+class FileManagerPrivateGetStringsFunction : public UIThreadExtensionFunction {
  public:
   DECLARE_EXTENSION_FUNCTION("fileManagerPrivate.getStrings",
                              FILEMANAGERPRIVATE_GETSTRINGS)
 
   FileManagerPrivateGetStringsFunction();
 
  protected:
   ~FileManagerPrivateGetStringsFunction() override;
 
-  // SyncExtensionFunction overrides.
-  bool RunSync() override;
+  // ExtensionFunction:
+  ResponseAction Run() override;
 };
 
 }  // namespace extensions
 
 #endif  // CHROME_BROWSER_CHROMEOS_EXTENSIONS_FILE_MANAGER_PRIVATE_API_STRINGS_H_