Unify BindState refcount management into the bound arguments.

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 37 matching lines @@
 
 namespace internal {
 
 // Don't use Alias Template directly here to avoid a compile error on MSVC2013.
 template <typename Functor, typename... Args>
 struct MakeUnboundRunTypeImpl {
   using Type =
       typename BindState<
           typename FunctorTraits<Functor>::RunnableType,
           typename FunctorTraits<Functor>::RunType,
-          typename std::decay<Args>::type...>::UnboundRunType;
+          Args...>::UnboundRunType;
 };
 
 }  // namespace internal
 
 template <typename Functor, typename... Args>
 using MakeUnboundRunType =
     typename internal::MakeUnboundRunTypeImpl<Functor, Args...>::Type;
 
 template <typename Functor, typename... Args>
 base::Callback<MakeUnboundRunType<Functor, Args...>>
@@ skipping 24 matching lines @@
   // For methods, we need to be careful for parameter 1.  We do not require
   // a scoped_refptr because BindState<> itself takes care of AddRef() for
   // methods. We also disallow binding of an array as the method's target
   // object.
   static_assert(!internal::BindsArrayToFirstArg<is_method, Args...>::value,
                 "first bound argument to method cannot be array");
   static_assert(
       !internal::HasRefCountedParamAsRawPtr<is_method, Args...>::value,
       "a parameter is a refcounted type and needs scoped_refptr");
 
-  using BindState = internal::BindState<
-      RunnableType, RunType, typename std::decay<Args>::type...>;
+  using BindState = internal::BindState<RunnableType, RunType, Args...>;
 
   return Callback<typename BindState::UnboundRunType>(
       new BindState(internal::MakeRunnable(functor),
                     std::forward<Args>(args)...));
 }
 
 }  // namespace base
 
 #endif  // BASE_BIND_H_