Redesigned and refactored ScopedMTPDeviceMapEntry, MTPDeviceMapService & MTPDeviceDelegate classes.

webkit/fileapi/file_system_operation_context.h

 // Copyright (c) 2012 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 WEBKIT_FILEAPI_FILE_SYSTEM_OPERATION_CONTEXT_H_
 #define WEBKIT_FILEAPI_FILE_SYSTEM_OPERATION_CONTEXT_H_
 
 #include "base/memory/ref_counted.h"
+#include "base/memory/weak_ptr.h"
 #include "webkit/fileapi/file_system_context.h"
 #include "webkit/fileapi/media/mtp_device_file_system_config.h"
 #include "webkit/fileapi/task_runner_bound_observer_list.h"
 #include "webkit/storage/webkit_storage_export.h"
 
 #if defined(SUPPORT_MTP_DEVICE_FILESYSTEM)
 #include "webkit/fileapi/media/mtp_device_delegate.h"
 #endif
 
 namespace base {
@@ skipping 13 matching lines @@
     return file_system_context_.get();
   }
 
   void set_allowed_bytes_growth(const int64& allowed_bytes_growth) {
     allowed_bytes_growth_ = allowed_bytes_growth;
   }
   int64 allowed_bytes_growth() const { return allowed_bytes_growth_; }
 
 #if defined(SUPPORT_MTP_DEVICE_FILESYSTEM)
   void set_mtp_device_delegate(MTPDeviceDelegate* delegate) {
-    mtp_device_delegate_ = delegate;
+    mtp_device_delegate_ = delegate->GetAsWeakPtrOnIOThread();
   }
 
-  MTPDeviceDelegate* mtp_device_delegate() const {
-    return mtp_device_delegate_.get();
+  base::WeakPtr<MTPDeviceDelegate> mtp_device_delegate() const {

[kinuko, 2012/11/15 10:23:39]

I'm afraid this weakptr is created on IO thread but may be accessed on FILE
thread.

[kmadhusu, 2012/11/15 17:52:24]

Can you please provide more details on how this can be accessed on FILE thread?

When I tested the code, I didn't not hit any invalid thread access error.
WeakPtr thread checker seems to be happy. As you said, I create the WeakPtr
@line 43. "delegate->GetAsWeakPtrOnIOThread()" detaches the weak pointer from IO
thread. I thought we dereference this weak pointer only in
device_media_file_util which is called on media sequenced task runner thread. 

+    return mtp_device_delegate_;
   }
 #endif
 
   // Returns TaskRunner which the operation is performed on.
   base::SequencedTaskRunner* task_runner() const {
     return task_runner_.get();
   }
 
   // Overrides TaskRunner which the operation is performed on.
   // file_system_context_->task_runners()->file_task_runner() is used otherwise.
@@ skipping 28 matching lines @@
 
   int64 allowed_bytes_growth_;
   MediaPathFilter* media_path_filter_;
 
   AccessObserverList access_observers_;
   ChangeObserverList change_observers_;
   UpdateObserverList update_observers_;
 
 #if defined(SUPPORT_MTP_DEVICE_FILESYSTEM)
   // Store the current mtp device delegate.
-  scoped_refptr<MTPDeviceDelegate> mtp_device_delegate_;
+  base::WeakPtr<MTPDeviceDelegate> mtp_device_delegate_;
 #endif
 };
 
 }  // namespace fileapi
 
 #endif  // WEBKIT_FILEAPI_FILE_SYSTEM_OPERATION_CONTEXT_H_