[fsp] Add support for truncating files.

chrome/browser/chromeos/file_system_provider/provided_file_system.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_FILE_SYSTEM_PROVIDER_PROVIDED_FILE_SYSTEM_H_
 #define CHROME_BROWSER_CHROMEOS_FILE_SYSTEM_PROVIDER_PROVIDED_FILE_SYSTEM_H_
 
 #include "base/memory/weak_ptr.h"
 #include "chrome/browser/chromeos/file_system_provider/provided_file_system_info.h"
 #include "chrome/browser/chromeos/file_system_provider/provided_file_system_interface.h"
@@ skipping 59 matching lines @@
       const base::FilePath& file_path,
       const fileapi::AsyncFileUtil::StatusCallback& callback) OVERRIDE;
   virtual void CopyEntry(
       const base::FilePath& source_path,
       const base::FilePath& target_path,
       const fileapi::AsyncFileUtil::StatusCallback& callback) OVERRIDE;
   virtual void MoveEntry(
       const base::FilePath& source_path,
       const base::FilePath& target_path,
       const fileapi::AsyncFileUtil::StatusCallback& callback) OVERRIDE;
+  virtual void Truncate(
+      const base::FilePath& file_path,
+      int64 length,
+      const fileapi::AsyncFileUtil::StatusCallback& callback) OVERRIDE;
   virtual const ProvidedFileSystemInfo& GetFileSystemInfo() const OVERRIDE;
   virtual RequestManager* GetRequestManager() OVERRIDE;
   virtual base::WeakPtr<ProvidedFileSystemInterface> GetWeakPtr() OVERRIDE;
 
  private:
   Profile* profile_;                       // Not owned.
   extensions::EventRouter* event_router_;  // Not owned. May be NULL.
   ProvidedFileSystemInfo file_system_info_;
   scoped_ptr<NotificationManagerInterface> notification_manager_;
   RequestManager request_manager_;
 
   base::WeakPtrFactory<ProvidedFileSystemInterface> weak_ptr_factory_;
   DISALLOW_COPY_AND_ASSIGN(ProvidedFileSystem);
 };
 
 }  // namespace file_system_provider
 }  // namespace chromeos
 
 #endif  // CHROME_BROWSER_CHROMEOS_FILE_SYSTEM_PROVIDER_PROVIDED_FILE_SYSTEM_H_