[fsp] Add FileStreamReader for the reading operation.

chrome/browser/chromeos/file_system_provider/provided_file_system_interface.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_INTERFACE_H_
 #define CHROME_BROWSER_CHROMEOS_FILE_SYSTEM_PROVIDER_PROVIDED_FILE_SYSTEM_INTERFACE_H_
 
 #include "base/callback.h"
 #include "base/files/file.h"
 #include "base/files/file_path.h"
+#include "base/memory/weak_ptr.h"
 #include "webkit/browser/fileapi/async_file_util.h"
 
 class EventRouter;
 
 namespace net {
 class IOBuffer;
 }  // namespace net
 
 namespace chromeos {
 namespace file_system_provider {
@@ skipping 56 matching lines @@
                         net::IOBuffer* buffer,
                         int64 offset,
                         int length,
                         const ReadChunkReceivedCallback& callback) = 0;
 
   // Returns a provided file system info for this file system.
   virtual const ProvidedFileSystemInfo& GetFileSystemInfo() const = 0;
 
   // Returns a request manager for the file system.
   virtual RequestManager* GetRequestManager() = 0;
+
+  // Returns a weak pointer to this object.
+  virtual base::WeakPtr<ProvidedFileSystemInterface> GetWeakPtr() = 0;
 };
 
 }  // namespace file_system_provider
 }  // namespace chromeos
 
 #endif  // CHROME_BROWSER_CHROMEOS_FILE_SYSTEM_PROVIDER_PROVIDED_FILE_SYSTEM_INTERFACE_H_