Introduce OnceClosure and BindOnce

base/bind.h

Index: base/bind.h
diff --git a/base/bind.h b/base/bind.h
index 9cf65b67764b0cbcb393cd392f6fdb480d57496b..905ad4891a0c3debd00eabeb8793ad068a5f7f47 100644
--- a/base/bind.h
+++ b/base/bind.h
@@ -11,7 +11,7 @@
 // Usage documentation
 // -----------------------------------------------------------------------------
 //
-// See base/callback.h for documentation.
+// See //docs/callback.md for documentation.
 //
 //
 // -----------------------------------------------------------------------------
@@ -23,21 +23,48 @@
 // terms and concepts.
 
 namespace base {
+namespace internal {
 
+// Bind as RepeatingCallback.
 template <typename Functor, typename... Args>
-inline base::Callback<MakeUnboundRunType<Functor, Args...>> Bind(
-    Functor&& functor,
-    Args&&... args) {
+inline RepeatingCallback<MakeUnboundRunType<Functor, Args...>>
+BindRepeating(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 = RepeatingCallback<UnboundRunType>;
   return CallbackType(new BindState(std::forward<Functor>(functor),
                                     std::forward<Args>(args)...),
                       &Invoker::Run);
 }
 
+// Bind as OnceCallback.
+template <typename Functor, typename... Args>
+inline OnceCallback<MakeUnboundRunType<Functor, Args...>>
+BindOnce(Functor&& functor, Args&&... args) {
+  using BindState = internal::MakeBindStateType<Functor, Args...>;
+  using UnboundRunType = MakeUnboundRunType<Functor, Args...>;
+  using Invoker = internal::Invoker<BindState, UnboundRunType>;
+
+  using CallbackType = OnceCallback<UnboundRunType>;
+  return CallbackType(new BindState(std::forward<Functor>(functor),
+                                    std::forward<Args>(args)...),
+                      &Invoker::RunOnce);
+}
+
+}  // namespace internal
+
+// Unannotated Bind.
+// TODO(tzik): Deprecate this and migrate to OnceCallback and
+// RepeatingCallback, once they get ready.
+template <typename Functor, typename... Args>
+inline Callback<MakeUnboundRunType<Functor, Args...>>
+Bind(Functor&& functor, Args&&... args) {
+  return internal::BindRepeating(std::forward<Functor>(functor),
+                                 std::forward<Args>(args)...);
+}
+
 }  // namespace base
 
 #endif  // BASE_BIND_H_