Move CallbackBase::polymorphic_invoke_ into BindStateBase

base/bind.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_BIND_H_
 #define BASE_BIND_H_
 
 #include "base/bind_internal.h"
 
 // -----------------------------------------------------------------------------
@@ skipping 13 matching lines @@
 
 namespace base {
 
 template <typename Functor, typename... Args>
 inline base::Callback<MakeUnboundRunType<Functor, Args...>> Bind(
     Functor&& functor,
     Args&&... args) {
   using BindState = internal::MakeBindStateType<Functor, Args...>;
   using UnboundRunType = MakeUnboundRunType<Functor, Args...>;
   using Invoker = internal::Invoker<BindState, UnboundRunType>;
+  using CallbackType = Callback<UnboundRunType>;
 
-  using CallbackType = Callback<UnboundRunType>;
-  return CallbackType(new BindState(std::forward<Functor>(functor),
-                                    std::forward<Args>(args)...),
-                      &Invoker::Run);
+  // Store the invoke func into PolymorphicInvoke before casting it to
+  // InvokeFuncStorage, so that we can ensure its type matches to
+  // PolymorphicInvoke, to which CallbackType will cast back.
+  using PolymorphicInvoke = typename CallbackType::PolymorphicInvoke;
+  PolymorphicInvoke invoke_func = &Invoker::Run;
+
+  using InvokeFuncStorage = internal::BindStateBase::InvokeFuncStorage;
+  return CallbackType(new BindState(
+      reinterpret_cast<InvokeFuncStorage>(invoke_func),
+      std::forward<Functor>(functor),
+      std::forward<Args>(args)...));
 }
 
 }  // namespace base
 
 #endif  // BASE_BIND_H_