Clean up base::Callback stuff

base/bind_internal.h

Index: base/bind_internal.h
diff --git a/base/bind_internal.h b/base/bind_internal.h
index c6832e6a479ed3da0a386855327de207e6fedca6..49ce0ed66d6ea87daf8e60802f319ea29890924f 100644
--- a/base/bind_internal.h
+++ b/base/bind_internal.h
@@ -39,12 +39,7 @@ namespace internal {
 //             even if the invocation syntax differs.
 //  RunType -- A function type (as opposed to function _pointer_ type) for
 //             a Run() function.  Usually just a convenience typedef.
-//  (Bound)ArgsType -- A function type that is being (ab)used to store the
-//                     types of set of arguments.  The "return" type is always
-//                     void here.  We use this hack so that we do not need
-//                     a new type name for each arity of type. (eg.,
-//                     BindState1, BindState2).  This makes forward
-//                     declarations and friending much much easier.
+//  (Bound)Args -- A set of types that stores the arguments.
 //
 // Types:
 //  RunnableAdapter<> -- Wraps the various "function" pointer types into an
@@ -56,7 +51,6 @@ namespace internal {
 //                     signature adapters are applied.
 //  MakeRunnable<> -- Takes a Functor and returns an object in the Runnable
 //                    type class that represents the underlying Functor.
-//                    There are |O(1)| MakeRunnable types.
 //  InvokeHelper<> -- Take a Runnable + arguments and actully invokes it.
 //                    Handle the differing syntaxes needed for WeakPtr<>
 //                    support, and for ignoring return values.  This is separate
@@ -360,19 +354,18 @@ struct Invoker<IndexSequence<bound_indices...>,
 // Normally, this is the same as the RunType of the Runnable, but it can
 // be different if an adapter like IgnoreResult() has been used.
 //
-// BoundArgsType contains the storage type for all the bound arguments by
-// (ab)using a function type.
-template <typename Runnable, typename RunType, typename BoundArgList>
+// BoundArgs contains the storage type for all the bound arguments.
+template <typename Runnable, typename RunType, typename... BoundArgs>
 struct BindState;
 
 template <typename Runnable,
           typename R,
           typename... Args,
           typename... BoundArgs>
-struct BindState<Runnable, R(Args...), TypeList<BoundArgs...>> final
+struct BindState<Runnable, R(Args...), BoundArgs...> final
     : public BindStateBase {
  private:
-  using StorageType = BindState<Runnable, R(Args...), TypeList<BoundArgs...>>;
+  using StorageType = BindState<Runnable, R(Args...), BoundArgs...>;
   using RunnableType = Runnable;
 
   // true_type if Runnable is a method invocation and the first bound argument