[WIP][Base] Use variadic template for Callback and Bind

base/bind_helpers.h

Index: base/bind_helpers.h
diff --git a/base/bind_helpers.h b/base/bind_helpers.h
index f3efc31953c78b349bf1b7e2d23c802129f54ac9..af6f8ac6ca312587d2f9dab3d5c02eb21748000c 100644
--- a/base/bind_helpers.h
+++ b/base/bind_helpers.h
@@ -435,45 +435,44 @@ struct UnwrapTraits<PassedWrapper<T> > {
 
 // Utility for handling different refcounting semantics in the Bind()
 // function.
-template <bool is_method, typename T>
-struct MaybeRefcount;
+template <bool is_method, typename... T>
+struct MaybeScopedRefPtr;
 
-template <typename T>
-struct MaybeRefcount<false, T> {
-  static void AddRef(const T&) {}
-  static void Release(const T&) {}
+template <bool is_method>
+struct MaybeScopedRefPtr<is_method> {
+  MaybeScopedRefPtr() {}
 };
 
-template <typename T, size_t n>
-struct MaybeRefcount<false, T[n]> {
-  static void AddRef(const T*) {}
-  static void Release(const T*) {}
+template <typename T, typename... Rest>
+struct MaybeScopedRefPtr<false, T, Rest...> {
+  MaybeScopedRefPtr(const T&, const Rest&...) {}
 };
 
-template <typename T>
-struct MaybeRefcount<true, T> {
-  static void AddRef(const T&) {}
-  static void Release(const T&) {}
+template <typename T, size_t n, typename... Rest>
+struct MaybeScopedRefPtr<false, T[n], Rest...> {
+  MaybeScopedRefPtr(const T*, const Rest&...) {}
 };
 
-template <typename T>
-struct MaybeRefcount<true, T*> {
-  static void AddRef(T* o) { o->AddRef(); }
-  static void Release(T* o) { o->Release(); }
+template <typename T, typename... Rest>
+struct MaybeScopedRefPtr<true, T, Rest...> {
+  MaybeScopedRefPtr(const T& o, const Rest&...) {}
 };
 
-// No need to additionally AddRef() and Release() since we are storing a
-// scoped_refptr<> inside the storage object already.
-template <typename T>
-struct MaybeRefcount<true, scoped_refptr<T> > {
-  static void AddRef(const scoped_refptr<T>& o) {}
-  static void Release(const scoped_refptr<T>& o) {}
+template <typename T, typename... Rest>
+struct MaybeScopedRefPtr<true, T*, Rest...> {
+  MaybeScopedRefPtr(T* o, const Rest&...) : ref_(o) {}
+  scoped_refptr<T> ref_;
 };
 
-template <typename T>
-struct MaybeRefcount<true, const T*> {
-  static void AddRef(const T* o) { o->AddRef(); }
-  static void Release(const T* o) { o->Release(); }
+template <typename T, typename... Rest>
+struct MaybeScopedRefPtr<true, scoped_refptr<T>, Rest...> {
+  MaybeScopedRefPtr(const scoped_refptr<T>&, const Rest&...) {}
+};
+
+template <typename T, typename... Rest>
+struct MaybeScopedRefPtr<true, const T*, Rest...> {
+  MaybeScopedRefPtr(const T* o, const Rest&...) : ref_(o) {}
+  scoped_refptr<const T> ref_;
 };
 
 // IsWeakMethod is a helper that determine if we are binding a WeakPtr<> to a
@@ -482,14 +481,15 @@ struct MaybeRefcount<true, const T*> {
 // the target object is invalidated.
 //
 // P1 should be the type of the object that will be received of the method.
-template <bool IsMethod, typename P1>
+template <bool IsMethod, typename... Args>
 struct IsWeakMethod : public false_type {};
 
-template <typename T>
-struct IsWeakMethod<true, WeakPtr<T> > : public true_type {};
+template <typename T, typename... Args>
+struct IsWeakMethod<true, WeakPtr<T>, Args...> : public true_type {};
 
-template <typename T>
-struct IsWeakMethod<true, ConstRefWrapper<WeakPtr<T> > > : public true_type {};
+template <typename T, typename... Args>
+struct IsWeakMethod<true, ConstRefWrapper<WeakPtr<T> >, Args...>
+    : public true_type {};
 
 }  // namespace internal