Introduce OnceClosure and BindOnce

base/bind.h

Index: base/bind.h
diff --git a/base/bind.h b/base/bind.h
index 86f624e49c80ae376112a73f88ef007e44d7342c..ec707a0618f288431e373ffe56b3813c409754a3 100644
--- a/base/bind.h
+++ b/base/bind.h
@@ -23,15 +23,38 @@
 // terms and concepts.
 
 namespace base {
+namespace internal {
 
+// Bind as OnceCallback.
 template <typename Functor, typename... Args>
-inline base::Callback<MakeUnboundRunType<Functor, Args...>> Bind(
-    Functor&& functor,
-    Args&&... 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 = Callback<UnboundRunType>;
+  using CallbackType = OnceCallback<UnboundRunType>;
+
+  // 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::RunOnce;
+
+  using InvokeFuncStorage = internal::BindStateBase::InvokeFuncStorage;
+  return CallbackType(new BindState(
+      reinterpret_cast<InvokeFuncStorage>(invoke_func),
+      std::forward<Functor>(functor),
+      std::forward<Args>(args)...));
+}
+
+// Bind as RepeatingCallback.
+template <typename Functor, typename... 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 = RepeatingCallback<UnboundRunType>;
 
   // Store the invoke func into PolymorphicInvoke before casting it to
   // InvokeFuncStorage, so that we can ensure its type matches to
@@ -46,6 +69,18 @@ inline base::Callback<MakeUnboundRunType<Functor, Args...>> Bind(
       std::forward<Args>(args)...));
 }
 
+}  // 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_