Drive extension functions from ExtensionFunction::Run. The

chrome/browser/chromeos/extensions/file_system_provider/provider_function.h

 // Copyright 2014 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_FILE_SYSTEM_PROVIDER_PROVIDER_FUNCTION_H_
 #define CHROME_BROWSER_CHROMEOS_EXTENSIONS_FILE_SYSTEM_PROVIDER_PROVIDER_FUNCTION_H_
 #include <string>
 
 #include "base/files/file.h"
 #include "base/memory/scoped_ptr.h"
@@ skipping 50 matching lines @@
   void RejectRequest(base::File::Error error);
 
   // Fulfills the request with parsed arguments of this API function
   // encapsulated as a RequestValue instance. Also, sets a response.
   // If |has_next| is set to true, then the function will be called again for
   // this request.
   void FulfillRequest(
       scoped_ptr<chromeos::file_system_provider::RequestValue> value,
       bool has_next);
 
-  // ChromeSyncExtensionFunction overrides.
-  virtual bool RunImpl() OVERRIDE;
+  // Subclasses implement this for their functionality.
+  // Called after Parse() is successful, such that |request_id_| and
+  // |request_manager_| have been fully initialized.
+  virtual bool RunWhenValid() = 0;
 
  private:
+  // ChromeSyncExtensionFunction overrides.
+  virtual bool RunSync() OVERRIDE;
+
   // Parses the request in order to extract the request manager. If fails, then
   // sets a response and returns false.
   bool Parse();
 
   // Sets an error message in case of a failure.
   void SetErrorResponse(const std::string& name, const std::string& message);
 
   int request_id_;
   chromeos::file_system_provider::RequestManager* request_manager_;
 };
 
 }  // namespace extensions
 
 #endif  // CHROME_BROWSER_CHROMEOS_EXTENSIONS_FILE_SYSTEM_PROVIDER_PROVIDER_FUNCTION_H_