Replace typedef with using for Callback/Bind related files

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"
 #include "base/callback_internal.h"
 
@@ skipping 37 matching lines @@
 namespace base {
 
 template <typename Functor, typename... Args>
 base::Callback<
     typename internal::BindState<
         typename internal::FunctorTraits<Functor>::RunnableType,
         typename internal::FunctorTraits<Functor>::RunType,
         typename internal::CallbackParamTraits<Args>::StorageType...>
             ::UnboundRunType>
 Bind(Functor functor, const Args&... args) {
-  // Typedefs for how to store and run the functor.
-  typedef typename internal::FunctorTraits<Functor>::RunnableType RunnableType;
-  typedef typename internal::FunctorTraits<Functor>::RunType RunType;
+  // Type aliases for how to store and run the functor.
+  using RunnableType = typename internal::FunctorTraits<Functor>::RunnableType;
+  using RunType = typename internal::FunctorTraits<Functor>::RunType;
 
   // Use RunnableType::RunType instead of RunType above because our
-  // checks should below for bound references need to know what the actual
+  // checks below for bound references need to know what the actual
   // functor is going to interpret the argument as.
-  typedef typename RunnableType::RunType BoundRunType;
+  using BoundRunType = typename RunnableType::RunType;
 
   using BoundArgs =
       internal::TakeTypeListItem<sizeof...(Args),
                                  internal::ExtractArgs<BoundRunType>>;
 
   // Do not allow binding a non-const reference parameter. Non-const reference
   // parameters are disallowed by the Google style guide.  Also, binding a
   // non-const reference parameter can make for subtle bugs because the
   // invoked function will receive a reference to the stored copy of the
   // argument and not the original.
   static_assert(!internal::HasNonConstReferenceItem<BoundArgs>::value,
                 "do not bind functions with nonconst ref");
 
   const bool is_method = internal::HasIsMethodTag<RunnableType>::value;
 
   // 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");
 
-  typedef internal::BindState<
+  using BindState = internal::BindState<
       RunnableType, RunType,
-      typename internal::CallbackParamTraits<Args>::StorageType...>
-      BindState;
+      typename internal::CallbackParamTraits<Args>::StorageType...>;
 
   return Callback<typename BindState::UnboundRunType>(
       new BindState(internal::MakeRunnable(functor), args...));
 }
 
 }  // namespace base
 
 #endif  // BASE_BIND_H_