Replace MessageLoop::DeleteSoon implementation with one that uses base::Bind.

base/message_loop_helpers.h

+// Copyright (c) 2011 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 BASE_MESSAGE_LOOP_HELPERS_H_
+#define BASE_MESSAGE_LOOP_HELPERS_H_
+#pragma once
+
+#include "base/basictypes.h"
+
+namespace tracked_objects {
+class Location;
+}
+
+namespace base {
+
+namespace subtle {
+template <class T, class R> class DeleteHelperInternal;
+}
+
+// This is a template helper which uses a function indirection to erase T from
+// the function signature while still remembering it so we can call the correct
+// destructor. We use this trick so we don't need to include bind.h in a
+// header file. We also embed the function in a class to make it easier for
+// users of DeleteSoon to declare the helper as a friend.
+template <class T>
+class DeleteHelper {
+ private:
+  // TODO(dcheng): Move the return type back to a function template parameter.
+  template <class T2, class R> friend class subtle::DeleteHelperInternal;
+
+  static void DoDelete(const void* object) {
+    delete reinterpret_cast<const T*>(object);
+  }
+
+  DISALLOW_COPY_AND_ASSIGN(DeleteHelper);
+};
+
+namespace subtle {
+
+// An internal MessageLoop-like class helper for DeleteHelper. We don't want to
+// expose DoDelete directly since the void* argument makes it possible to pass
+// an object of the wrong type to delete. Instead, we force callers to go
+// through DeleteHelperInternal for type safety. MessageLoop-like classes which
+// expose a DeleteSoon method should friend this class and implement a
+// DeleteSoonInternal method with the following signature:
+// bool(const tracked_objects::Location&,
+//      void(*deleter)(const void*),
+//      void* object)
+// An implementation of DeleteSoonInternal should simply create a base::Closure
+// from (deleter, object) and return the result of posting the task.
+template <class T, class ReturnType>
+class DeleteHelperInternal {
+ public:
+  template <class MessageLoopType>
+  static ReturnType DeleteOnMessageLoop(
+      MessageLoopType* message_loop,
+      const tracked_objects::Location& from_here,
+      const T* object) {
+    return message_loop->DeleteSoonInternal(from_here,
+                                            &DeleteHelper<T>::DoDelete,
+                                            object);
+  }
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(DeleteHelperInternal);
+};
+
+}  // namespace subtle
+
+}  // namespace base
+
+#endif  // BASE_MESSAGE_LOOP_HELPERS_H_