Redesigned and refactored ScopedMTPDeviceMapEntry, MTPDeviceMapService & MTPDeviceDelegate classes.

webkit/fileapi/file_system_operation_context.h

Index: webkit/fileapi/file_system_operation_context.h
diff --git a/webkit/fileapi/file_system_operation_context.h b/webkit/fileapi/file_system_operation_context.h
index 067e0d8886b81dd64345fd19e3767233c92b8e7e..932ba323ba826ce3966a14d6b52f51af0e488388 100644
--- a/webkit/fileapi/file_system_operation_context.h
+++ b/webkit/fileapi/file_system_operation_context.h
@@ -6,6 +6,7 @@
 #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"
@@ -38,12 +39,15 @@ class WEBKIT_STORAGE_EXPORT_PRIVATE FileSystemOperationContext {
   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
 
@@ -91,8 +95,9 @@ class WEBKIT_STORAGE_EXPORT_PRIVATE FileSystemOperationContext {
   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
 };