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 12 matching lines @@
   FileSystemContext* file_system_context() const {
     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)
+  // Called on IO thread.
   void set_mtp_device_delegate(MTPDeviceDelegate* delegate) {
-    mtp_device_delegate_ = delegate;
+    mtp_device_delegate_ = delegate->GetAsWeakPtrOnIOThread();

[Lei Zhang, 2012/11/21 01:33:30]

This is no longer a simple setter if you call GetAsWeakPtrOnIOThread(). There's
only one set_mtp_device_delegate() caller, so can we call
GetAsWeakPtrOnIOThread() there instead?

[kmadhusu, 2012/11/21 04:09:53]

sure. Done.

   }
 
-  MTPDeviceDelegate* mtp_device_delegate() const {
-    return mtp_device_delegate_.get();
+  // Caller of this function should dereference the delegate only on media
+  // sequenced task runner thread.
+  base::WeakPtr<MTPDeviceDelegate> mtp_device_delegate() const {
+    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 27 matching lines @@
   scoped_refptr<base::SequencedTaskRunner> task_runner_;
 
   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_;
+  // The media transfer protocol(MTP) device delegate.
+  // Set on IO thread and dereferenced on media sequenced task runner thread.
+  base::WeakPtr<MTPDeviceDelegate> mtp_device_delegate_;
 #endif
 };
 
 }  // namespace fileapi
 
 #endif  // WEBKIT_FILEAPI_FILE_SYSTEM_OPERATION_CONTEXT_H_