Extend base::Callback to 8 arguments.

This is required by the Android port in order to support using base::Bind with
the FaviconService::GetRawFaviconForURL method. This is used in code yet in process of being upstreamed (bug 138755).

BUG=146003


Review URL: https://chromiumcodereview.appspot.com/10919055

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@154885 0039d316-1c4b-4281-b951-d872f2087c98

4 files changed, 852 insertions, 1 deletions

diff --git a/base/bind.h b/base/bind.h
index 5cf124d..3682150 100644
--- a/base/bind.h
+++ b/base/bind.h
@@ -512,6 +512,90 @@ Bind(Functor functor, const P1& p1, const P2& p2, const P3& p3, const P4& p4,
           p7));
 }
 
+template <typename Functor, typename P1, typename P2, typename P3, typename P4,
+    typename P5, typename P6, typename P7, typename P8>
+base::Callback<
+    typename internal::BindState<
+        typename internal::FunctorTraits<Functor>::RunnableType,
+        typename internal::FunctorTraits<Functor>::RunType,
+        void(typename internal::CallbackParamTraits<P1>::StorageType,
+            typename internal::CallbackParamTraits<P2>::StorageType,
+            typename internal::CallbackParamTraits<P3>::StorageType,
+            typename internal::CallbackParamTraits<P4>::StorageType,
+            typename internal::CallbackParamTraits<P5>::StorageType,
+            typename internal::CallbackParamTraits<P6>::StorageType,
+            typename internal::CallbackParamTraits<P7>::StorageType,
+            typename internal::CallbackParamTraits<P8>::StorageType)>
+            ::UnboundRunType>
+Bind(Functor functor, const P1& p1, const P2& p2, const P3& p3, const P4& p4,
+    const P5& p5, const P6& p6, const P7& p7, const P8& p8) {
+  // Typedefs for how to store and run the functor.
+  typedef typename internal::FunctorTraits<Functor>::RunnableType RunnableType;
+  typedef typename internal::FunctorTraits<Functor>::RunType RunType;
+
+  // Use RunnableType::RunType instead of RunType above because our
+  // checks should below for bound references need to know what the actual
+  // functor is going to interpret the argument as.
+  typedef internal::FunctionTraits<typename RunnableType::RunType>
+      BoundFunctorTraits;
+
+  // 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.
+  COMPILE_ASSERT(
+      !(is_non_const_reference<typename BoundFunctorTraits::A1Type>::value ||
+          is_non_const_reference<typename BoundFunctorTraits::A2Type>::value ||
+          is_non_const_reference<typename BoundFunctorTraits::A3Type>::value ||
+          is_non_const_reference<typename BoundFunctorTraits::A4Type>::value ||
+          is_non_const_reference<typename BoundFunctorTraits::A5Type>::value ||
+          is_non_const_reference<typename BoundFunctorTraits::A6Type>::value ||
+          is_non_const_reference<typename BoundFunctorTraits::A7Type>::value ||
+          is_non_const_reference<typename BoundFunctorTraits::A8Type>::value ),
+      do_not_bind_functions_with_nonconst_ref);
+
+  // 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.
+  COMPILE_ASSERT(
+      internal::HasIsMethodTag<RunnableType>::value ||
+          !internal::NeedsScopedRefptrButGetsRawPtr<P1>::value,
+      p1_is_refcounted_type_and_needs_scoped_refptr);
+  COMPILE_ASSERT(!internal::HasIsMethodTag<RunnableType>::value ||
+                     !is_array<P1>::value,
+                 first_bound_argument_to_method_cannot_be_array);
+  COMPILE_ASSERT(!internal::NeedsScopedRefptrButGetsRawPtr<P2>::value,
+                 p2_is_refcounted_type_and_needs_scoped_refptr);
+  COMPILE_ASSERT(!internal::NeedsScopedRefptrButGetsRawPtr<P3>::value,
+                 p3_is_refcounted_type_and_needs_scoped_refptr);
+  COMPILE_ASSERT(!internal::NeedsScopedRefptrButGetsRawPtr<P4>::value,
+                 p4_is_refcounted_type_and_needs_scoped_refptr);
+  COMPILE_ASSERT(!internal::NeedsScopedRefptrButGetsRawPtr<P5>::value,
+                 p5_is_refcounted_type_and_needs_scoped_refptr);
+  COMPILE_ASSERT(!internal::NeedsScopedRefptrButGetsRawPtr<P6>::value,
+                 p6_is_refcounted_type_and_needs_scoped_refptr);
+  COMPILE_ASSERT(!internal::NeedsScopedRefptrButGetsRawPtr<P7>::value,
+                 p7_is_refcounted_type_and_needs_scoped_refptr);
+  COMPILE_ASSERT(!internal::NeedsScopedRefptrButGetsRawPtr<P8>::value,
+                 p8_is_refcounted_type_and_needs_scoped_refptr);
+  typedef internal::BindState<RunnableType, RunType,
+      void(typename internal::CallbackParamTraits<P1>::StorageType,
+      typename internal::CallbackParamTraits<P2>::StorageType,
+      typename internal::CallbackParamTraits<P3>::StorageType,
+      typename internal::CallbackParamTraits<P4>::StorageType,
+      typename internal::CallbackParamTraits<P5>::StorageType,
+      typename internal::CallbackParamTraits<P6>::StorageType,
+      typename internal::CallbackParamTraits<P7>::StorageType,
+      typename internal::CallbackParamTraits<P8>::StorageType)> BindState;
+
+
+  return Callback<typename BindState::UnboundRunType>(
+      new BindState(internal::MakeRunnable(functor), p1, p2, p3, p4, p5, p6,
+          p7, p8));
+}
+
 }  // namespace base
 
 #endif  // BASE_BIND_H_
diff --git a/base/bind_internal.h b/base/bind_internal.h
index 4e155ab..3e7fa8b 100644
--- a/base/bind_internal.h
+++ b/base/bind_internal.h
@@ -644,6 +644,91 @@ class RunnableAdapter<R(T::*)(A1, A2, A3, A4, A5, A6, A7) const> {
   R (T::*method_)(A1, A2, A3, A4, A5, A6, A7) const;
 };
 
+// Function: Arity 8.
+template <typename R, typename A1, typename A2, typename A3, typename A4,
+    typename A5, typename A6, typename A7, typename A8>
+class RunnableAdapter<R(*)(A1, A2, A3, A4, A5, A6, A7, A8)> {
+ public:
+  typedef R (RunType)(A1, A2, A3, A4, A5, A6, A7, A8);
+
+  explicit RunnableAdapter(R(*function)(A1, A2, A3, A4, A5, A6, A7, A8))
+      : function_(function) {
+  }
+
+  R Run(typename CallbackParamTraits<A1>::ForwardType a1,
+      typename CallbackParamTraits<A2>::ForwardType a2,
+      typename CallbackParamTraits<A3>::ForwardType a3,
+      typename CallbackParamTraits<A4>::ForwardType a4,
+      typename CallbackParamTraits<A5>::ForwardType a5,
+      typename CallbackParamTraits<A6>::ForwardType a6,
+      typename CallbackParamTraits<A7>::ForwardType a7,
+      typename CallbackParamTraits<A8>::ForwardType a8) {
+    return function_(CallbackForward(a1), CallbackForward(a2),
+        CallbackForward(a3), CallbackForward(a4), CallbackForward(a5),
+        CallbackForward(a6), CallbackForward(a7), CallbackForward(a8));
+  }
+
+ private:
+  R (*function_)(A1, A2, A3, A4, A5, A6, A7, A8);
+};
+
+// Method: Arity 8.
+template <typename R, typename T, typename A1, typename A2, typename A3,
+    typename A4, typename A5, typename A6, typename A7, typename A8>
+class RunnableAdapter<R(T::*)(A1, A2, A3, A4, A5, A6, A7, A8)> {
+ public:
+  typedef R (RunType)(T*, A1, A2, A3, A4, A5, A6, A7, A8);
+  typedef true_type IsMethod;
+
+  explicit RunnableAdapter(R(T::*method)(A1, A2, A3, A4, A5, A6, A7, A8))
+      : method_(method) {
+  }
+
+  R Run(T* object, typename CallbackParamTraits<A1>::ForwardType a1,
+      typename CallbackParamTraits<A2>::ForwardType a2,
+      typename CallbackParamTraits<A3>::ForwardType a3,
+      typename CallbackParamTraits<A4>::ForwardType a4,
+      typename CallbackParamTraits<A5>::ForwardType a5,
+      typename CallbackParamTraits<A6>::ForwardType a6,
+      typename CallbackParamTraits<A7>::ForwardType a7,
+      typename CallbackParamTraits<A8>::ForwardType a8) {
+    return (object->*method_)(CallbackForward(a1), CallbackForward(a2),
+        CallbackForward(a3), CallbackForward(a4), CallbackForward(a5),
+        CallbackForward(a6), CallbackForward(a7), CallbackForward(a8));
+  }
+
+ private:
+  R (T::*method_)(A1, A2, A3, A4, A5, A6, A7, A8);
+};
+
+// Const Method: Arity 8.
+template <typename R, typename T, typename A1, typename A2, typename A3,
+    typename A4, typename A5, typename A6, typename A7, typename A8>
+class RunnableAdapter<R(T::*)(A1, A2, A3, A4, A5, A6, A7, A8) const> {
+ public:
+  typedef R (RunType)(const T*, A1, A2, A3, A4, A5, A6, A7, A8);
+  typedef true_type IsMethod;
+
+  explicit RunnableAdapter(R(T::*method)(A1, A2, A3, A4, A5, A6, A7, A8) const)
+      : method_(method) {
+  }
+
+  R Run(const T* object, typename CallbackParamTraits<A1>::ForwardType a1,
+      typename CallbackParamTraits<A2>::ForwardType a2,
+      typename CallbackParamTraits<A3>::ForwardType a3,
+      typename CallbackParamTraits<A4>::ForwardType a4,
+      typename CallbackParamTraits<A5>::ForwardType a5,
+      typename CallbackParamTraits<A6>::ForwardType a6,
+      typename CallbackParamTraits<A7>::ForwardType a7,
+      typename CallbackParamTraits<A8>::ForwardType a8) {
+    return (object->*method_)(CallbackForward(a1), CallbackForward(a2),
+        CallbackForward(a3), CallbackForward(a4), CallbackForward(a5),
+        CallbackForward(a6), CallbackForward(a7), CallbackForward(a8));
+  }
+
+ private:
+  R (T::*method_)(A1, A2, A3, A4, A5, A6, A7, A8) const;
+};
 
 // FunctionTraits<>
 //
@@ -722,6 +807,19 @@ struct FunctionTraits<R(A1, A2, A3, A4, A5, A6, A7)> {
   typedef A7 A7Type;
 };
 
+template <typename R, typename A1, typename A2, typename A3, typename A4,
+    typename A5, typename A6, typename A7, typename A8>
+struct FunctionTraits<R(A1, A2, A3, A4, A5, A6, A7, A8)> {
+  typedef R ReturnType;
+  typedef A1 A1Type;
+  typedef A2 A2Type;
+  typedef A3 A3Type;
+  typedef A4 A4Type;
+  typedef A5 A5Type;
+  typedef A6 A6Type;
+  typedef A7 A7Type;
+  typedef A8 A8Type;
+};
 
 // ForceVoidReturn<>
 //
@@ -772,6 +870,11 @@ struct ForceVoidReturn<R(A1, A2, A3, A4, A5, A6, A7)> {
   typedef void(RunType)(A1, A2, A3, A4, A5, A6, A7);
 };
 
+template <typename R, typename A1, typename A2, typename A3, typename A4,
+    typename A5, typename A6, typename A7, typename A8>
+struct ForceVoidReturn<R(A1, A2, A3, A4, A5, A6, A7, A8)> {
+  typedef void(RunType)(A1, A2, A3, A4, A5, A6, A7, A8);
+};
 
 // FunctorTraits<>
 //
@@ -1020,7 +1123,7 @@ struct InvokeHelper<false, ReturnType, Runnable,
   }
 };
 
-template <typename Runnable,typename A1, typename A2, typename A3, typename A4,
+template <typename Runnable, typename A1, typename A2, typename A3, typename A4,
     typename A5, typename A6>
 struct InvokeHelper<false, void, Runnable,
     void(A1, A2, A3, A4, A5, A6)>  {
@@ -1086,6 +1189,47 @@ struct InvokeHelper<true, void, Runnable,
   }
 };
 
+template <typename ReturnType, typename Runnable,typename A1, typename A2,
+    typename A3, typename A4, typename A5, typename A6, typename A7,
+    typename A8>
+struct InvokeHelper<false, ReturnType, Runnable,
+    void(A1, A2, A3, A4, A5, A6, A7, A8)>  {
+  static ReturnType MakeItSo(Runnable runnable, A1 a1, A2 a2, A3 a3, A4 a4,
+      A5 a5, A6 a6, A7 a7, A8 a8) {
+    return runnable.Run(CallbackForward(a1), CallbackForward(a2),
+        CallbackForward(a3), CallbackForward(a4), CallbackForward(a5),
+        CallbackForward(a6), CallbackForward(a7), CallbackForward(a8));
+  }
+};
+
+template <typename Runnable,typename A1, typename A2, typename A3, typename A4,
+    typename A5, typename A6, typename A7, typename A8>
+struct InvokeHelper<false, void, Runnable,
+    void(A1, A2, A3, A4, A5, A6, A7, A8)>  {
+  static void MakeItSo(Runnable runnable, A1 a1, A2 a2, A3 a3, A4 a4, A5 a5,
+      A6 a6, A7 a7, A8 a8) {
+    runnable.Run(CallbackForward(a1), CallbackForward(a2), CallbackForward(a3),
+        CallbackForward(a4), CallbackForward(a5), CallbackForward(a6),
+        CallbackForward(a7), CallbackForward(a8));
+  }
+};
+
+template <typename Runnable, typename A1, typename A2, typename A3,
+    typename A4, typename A5, typename A6, typename A7, typename A8>
+struct InvokeHelper<true, void, Runnable,
+    void(A1, A2, A3, A4, A5, A6, A7, A8)>  {
+  static void MakeItSo(Runnable runnable, A1 a1, A2 a2, A3 a3, A4 a4, A5 a5,
+      A6 a6, A7 a7, A8 a8) {
+    if (!a1.get()) {
+      return;
+    }
+
+    runnable.Run(CallbackForward(a1), CallbackForward(a2), CallbackForward(a3),
+        CallbackForward(a4), CallbackForward(a5), CallbackForward(a6),
+        CallbackForward(a7), CallbackForward(a8));
+  }
+};
+
 #if !defined(_MSC_VER)
 
 template <typename ReturnType, typename Runnable, typename ArgsType>
@@ -2518,6 +2662,491 @@ struct Invoker<7, StorageType, R(X1, X2, X3, X4, X5, X6, X7)> {
   }
 };
 
+// Arity 8 -> 8.
+template <typename StorageType, typename R,typename X1, typename X2,
+    typename X3, typename X4, typename X5, typename X6, typename X7,
+    typename X8>
+struct Invoker<0, StorageType, R(X1, X2, X3, X4, X5, X6, X7, X8)> {
+  typedef R(RunType)(BindStateBase*,
+      typename CallbackParamTraits<X1>::ForwardType,
+      typename CallbackParamTraits<X2>::ForwardType,
+      typename CallbackParamTraits<X3>::ForwardType,
+      typename CallbackParamTraits<X4>::ForwardType,
+      typename CallbackParamTraits<X5>::ForwardType,
+      typename CallbackParamTraits<X6>::ForwardType,
+      typename CallbackParamTraits<X7>::ForwardType,
+      typename CallbackParamTraits<X8>::ForwardType);
+
+  typedef R(UnboundRunType)(X1, X2, X3, X4, X5, X6, X7, X8);
+
+  static R Run(BindStateBase* base,
+      typename CallbackParamTraits<X1>::ForwardType x1,
+      typename CallbackParamTraits<X2>::ForwardType x2,
+      typename CallbackParamTraits<X3>::ForwardType x3,
+      typename CallbackParamTraits<X4>::ForwardType x4,
+      typename CallbackParamTraits<X5>::ForwardType x5,
+      typename CallbackParamTraits<X6>::ForwardType x6,
+      typename CallbackParamTraits<X7>::ForwardType x7,
+      typename CallbackParamTraits<X8>::ForwardType x8) {
+    StorageType* storage = static_cast<StorageType*>(base);
+
+    // Local references to make debugger stepping easier. If in a debugger,
+    // you really want to warp ahead and step through the
+    // InvokeHelper<>::MakeItSo() call below.
+
+    return InvokeHelper<StorageType::IsWeakCall::value, R,
+           typename StorageType::RunnableType,
+           void(typename CallbackParamTraits<X1>::ForwardType x1,
+               typename CallbackParamTraits<X2>::ForwardType x2,
+               typename CallbackParamTraits<X3>::ForwardType x3,
+               typename CallbackParamTraits<X4>::ForwardType x4,
+               typename CallbackParamTraits<X5>::ForwardType x5,
+               typename CallbackParamTraits<X6>::ForwardType x6,
+               typename CallbackParamTraits<X7>::ForwardType x7,
+               typename CallbackParamTraits<X8>::ForwardType x8)>
+               ::MakeItSo(storage->runnable_, CallbackForward(x1),
+                   CallbackForward(x2), CallbackForward(x3),
+                   CallbackForward(x4), CallbackForward(x5),
+                   CallbackForward(x6), CallbackForward(x7),
+                   CallbackForward(x8));
+  }
+};
+
+// Arity 8 -> 7.
+template <typename StorageType, typename R,typename X1, typename X2,
+    typename X3, typename X4, typename X5, typename X6, typename X7,
+    typename X8>
+struct Invoker<1, StorageType, R(X1, X2, X3, X4, X5, X6, X7, X8)> {
+  typedef R(RunType)(BindStateBase*,
+      typename CallbackParamTraits<X2>::ForwardType,
+      typename CallbackParamTraits<X3>::ForwardType,
+      typename CallbackParamTraits<X4>::ForwardType,
+      typename CallbackParamTraits<X5>::ForwardType,
+      typename CallbackParamTraits<X6>::ForwardType,
+      typename CallbackParamTraits<X7>::ForwardType,
+      typename CallbackParamTraits<X8>::ForwardType);
+
+  typedef R(UnboundRunType)(X2, X3, X4, X5, X6, X7, X8);
+
+  static R Run(BindStateBase* base,
+      typename CallbackParamTraits<X2>::ForwardType x2,
+      typename CallbackParamTraits<X3>::ForwardType x3,
+      typename CallbackParamTraits<X4>::ForwardType x4,
+      typename CallbackParamTraits<X5>::ForwardType x5,
+      typename CallbackParamTraits<X6>::ForwardType x6,
+      typename CallbackParamTraits<X7>::ForwardType x7,
+      typename CallbackParamTraits<X8>::ForwardType x8) {
+    StorageType* storage = static_cast<StorageType*>(base);
+
+    // Local references to make debugger stepping easier. If in a debugger,
+    // you really want to warp ahead and step through the
+    // InvokeHelper<>::MakeItSo() call below.
+    typedef typename StorageType::Bound1UnwrapTraits Bound1UnwrapTraits;
+
+    typename Bound1UnwrapTraits::ForwardType x1 =
+        Bound1UnwrapTraits::Unwrap(storage->p1_);
+    return InvokeHelper<StorageType::IsWeakCall::value, R,
+           typename StorageType::RunnableType,
+           void(typename Bound1UnwrapTraits::ForwardType,
+               typename CallbackParamTraits<X2>::ForwardType x2,
+               typename CallbackParamTraits<X3>::ForwardType x3,
+               typename CallbackParamTraits<X4>::ForwardType x4,
+               typename CallbackParamTraits<X5>::ForwardType x5,
+               typename CallbackParamTraits<X6>::ForwardType x6,
+               typename CallbackParamTraits<X7>::ForwardType x7,
+               typename CallbackParamTraits<X8>::ForwardType x8)>
+               ::MakeItSo(storage->runnable_, CallbackForward(x1),
+                   CallbackForward(x2), CallbackForward(x3),
+                   CallbackForward(x4), CallbackForward(x5),
+                   CallbackForward(x6), CallbackForward(x7),
+                   CallbackForward(x8));
+  }
+};
+
+// Arity 8 -> 6.
+template <typename StorageType, typename R,typename X1, typename X2,
+    typename X3, typename X4, typename X5, typename X6, typename X7,
+    typename X8>
+struct Invoker<2, StorageType, R(X1, X2, X3, X4, X5, X6, X7, X8)> {
+  typedef R(RunType)(BindStateBase*,
+      typename CallbackParamTraits<X3>::ForwardType,
+      typename CallbackParamTraits<X4>::ForwardType,
+      typename CallbackParamTraits<X5>::ForwardType,
+      typename CallbackParamTraits<X6>::ForwardType,
+      typename CallbackParamTraits<X7>::ForwardType,
+      typename CallbackParamTraits<X8>::ForwardType);
+
+  typedef R(UnboundRunType)(X3, X4, X5, X6, X7, X8);
+
+  static R Run(BindStateBase* base,
+      typename CallbackParamTraits<X3>::ForwardType x3,
+      typename CallbackParamTraits<X4>::ForwardType x4,
+      typename CallbackParamTraits<X5>::ForwardType x5,
+      typename CallbackParamTraits<X6>::ForwardType x6,
+      typename CallbackParamTraits<X7>::ForwardType x7,
+      typename CallbackParamTraits<X8>::ForwardType x8) {
+    StorageType* storage = static_cast<StorageType*>(base);
+
+    // Local references to make debugger stepping easier. If in a debugger,
+    // you really want to warp ahead and step through the
+    // InvokeHelper<>::MakeItSo() call below.
+    typedef typename StorageType::Bound1UnwrapTraits Bound1UnwrapTraits;
+    typedef typename StorageType::Bound2UnwrapTraits Bound2UnwrapTraits;
+
+    typename Bound1UnwrapTraits::ForwardType x1 =
+        Bound1UnwrapTraits::Unwrap(storage->p1_);
+    typename Bound2UnwrapTraits::ForwardType x2 =
+        Bound2UnwrapTraits::Unwrap(storage->p2_);
+    return InvokeHelper<StorageType::IsWeakCall::value, R,
+           typename StorageType::RunnableType,
+           void(typename Bound1UnwrapTraits::ForwardType,
+               typename Bound2UnwrapTraits::ForwardType,
+               typename CallbackParamTraits<X3>::ForwardType x3,
+               typename CallbackParamTraits<X4>::ForwardType x4,
+               typename CallbackParamTraits<X5>::ForwardType x5,
+               typename CallbackParamTraits<X6>::ForwardType x6,
+               typename CallbackParamTraits<X7>::ForwardType x7,
+               typename CallbackParamTraits<X8>::ForwardType x8)>
+               ::MakeItSo(storage->runnable_, CallbackForward(x1),
+                   CallbackForward(x2), CallbackForward(x3),
+                   CallbackForward(x4), CallbackForward(x5),
+                   CallbackForward(x6), CallbackForward(x7),
+                   CallbackForward(x8));
+  }
+};
+
+// Arity 8 -> 5.
+template <typename StorageType, typename R,typename X1, typename X2,
+    typename X3, typename X4, typename X5, typename X6, typename X7,
+    typename X8>
+struct Invoker<3, StorageType, R(X1, X2, X3, X4, X5, X6, X7, X8)> {
+  typedef R(RunType)(BindStateBase*,
+      typename CallbackParamTraits<X4>::ForwardType,
+      typename CallbackParamTraits<X5>::ForwardType,
+      typename CallbackParamTraits<X6>::ForwardType,
+      typename CallbackParamTraits<X7>::ForwardType,
+      typename CallbackParamTraits<X8>::ForwardType);
+
+  typedef R(UnboundRunType)(X4, X5, X6, X7, X8);
+
+  static R Run(BindStateBase* base,
+      typename CallbackParamTraits<X4>::ForwardType x4,
+      typename CallbackParamTraits<X5>::ForwardType x5,
+      typename CallbackParamTraits<X6>::ForwardType x6,
+      typename CallbackParamTraits<X7>::ForwardType x7,
+      typename CallbackParamTraits<X8>::ForwardType x8) {
+    StorageType* storage = static_cast<StorageType*>(base);
+
+    // Local references to make debugger stepping easier. If in a debugger,
+    // you really want to warp ahead and step through the
+    // InvokeHelper<>::MakeItSo() call below.
+    typedef typename StorageType::Bound1UnwrapTraits Bound1UnwrapTraits;
+    typedef typename StorageType::Bound2UnwrapTraits Bound2UnwrapTraits;
+    typedef typename StorageType::Bound3UnwrapTraits Bound3UnwrapTraits;
+
+    typename Bound1UnwrapTraits::ForwardType x1 =
+        Bound1UnwrapTraits::Unwrap(storage->p1_);
+    typename Bound2UnwrapTraits::ForwardType x2 =
+        Bound2UnwrapTraits::Unwrap(storage->p2_);
+    typename Bound3UnwrapTraits::ForwardType x3 =
+        Bound3UnwrapTraits::Unwrap(storage->p3_);
+    return InvokeHelper<StorageType::IsWeakCall::value, R,
+           typename StorageType::RunnableType,
+           void(typename Bound1UnwrapTraits::ForwardType,
+               typename Bound2UnwrapTraits::ForwardType,
+               typename Bound3UnwrapTraits::ForwardType,
+               typename CallbackParamTraits<X4>::ForwardType x4,
+               typename CallbackParamTraits<X5>::ForwardType x5,
+               typename CallbackParamTraits<X6>::ForwardType x6,
+               typename CallbackParamTraits<X7>::ForwardType x7,
+               typename CallbackParamTraits<X8>::ForwardType x8)>
+               ::MakeItSo(storage->runnable_, CallbackForward(x1),
+                   CallbackForward(x2), CallbackForward(x3),
+                   CallbackForward(x4), CallbackForward(x5),
+                   CallbackForward(x6), CallbackForward(x7),
+                   CallbackForward(x8));
+  }
+};
+
+// Arity 8 -> 4.
+template <typename StorageType, typename R,typename X1, typename X2,
+    typename X3, typename X4, typename X5, typename X6, typename X7,
+    typename X8>
+struct Invoker<4, StorageType, R(X1, X2, X3, X4, X5, X6, X7, X8)> {
+  typedef R(RunType)(BindStateBase*,
+      typename CallbackParamTraits<X5>::ForwardType,
+      typename CallbackParamTraits<X6>::ForwardType,
+      typename CallbackParamTraits<X7>::ForwardType,
+      typename CallbackParamTraits<X8>::ForwardType);
+
+  typedef R(UnboundRunType)(X5, X6, X7, X8);
+
+  static R Run(BindStateBase* base,
+      typename CallbackParamTraits<X5>::ForwardType x5,
+      typename CallbackParamTraits<X6>::ForwardType x6,
+      typename CallbackParamTraits<X7>::ForwardType x7,
+      typename CallbackParamTraits<X8>::ForwardType x8) {
+    StorageType* storage = static_cast<StorageType*>(base);
+
+    // Local references to make debugger stepping easier. If in a debugger,
+    // you really want to warp ahead and step through the
+    // InvokeHelper<>::MakeItSo() call below.
+    typedef typename StorageType::Bound1UnwrapTraits Bound1UnwrapTraits;
+    typedef typename StorageType::Bound2UnwrapTraits Bound2UnwrapTraits;
+    typedef typename StorageType::Bound3UnwrapTraits Bound3UnwrapTraits;
+    typedef typename StorageType::Bound4UnwrapTraits Bound4UnwrapTraits;
+
+    typename Bound1UnwrapTraits::ForwardType x1 =
+        Bound1UnwrapTraits::Unwrap(storage->p1_);
+    typename Bound2UnwrapTraits::ForwardType x2 =
+        Bound2UnwrapTraits::Unwrap(storage->p2_);
+    typename Bound3UnwrapTraits::ForwardType x3 =
+        Bound3UnwrapTraits::Unwrap(storage->p3_);
+    typename Bound4UnwrapTraits::ForwardType x4 =
+        Bound4UnwrapTraits::Unwrap(storage->p4_);
+    return InvokeHelper<StorageType::IsWeakCall::value, R,
+           typename StorageType::RunnableType,
+           void(typename Bound1UnwrapTraits::ForwardType,
+               typename Bound2UnwrapTraits::ForwardType,
+               typename Bound3UnwrapTraits::ForwardType,
+               typename Bound4UnwrapTraits::ForwardType,
+               typename CallbackParamTraits<X5>::ForwardType x5,
+               typename CallbackParamTraits<X6>::ForwardType x6,
+               typename CallbackParamTraits<X7>::ForwardType x7,
+               typename CallbackParamTraits<X8>::ForwardType x8)>
+               ::MakeItSo(storage->runnable_, CallbackForward(x1),
+                   CallbackForward(x2), CallbackForward(x3),
+                   CallbackForward(x4), CallbackForward(x5),
+                   CallbackForward(x6), CallbackForward(x7),
+                   CallbackForward(x8));
+  }
+};
+
+// Arity 8 -> 3.
+template <typename StorageType, typename R,typename X1, typename X2,
+    typename X3, typename X4, typename X5, typename X6, typename X7,
+    typename X8>
+struct Invoker<5, StorageType, R(X1, X2, X3, X4, X5, X6, X7, X8)> {
+  typedef R(RunType)(BindStateBase*,
+      typename CallbackParamTraits<X6>::ForwardType,
+      typename CallbackParamTraits<X7>::ForwardType,
+      typename CallbackParamTraits<X8>::ForwardType);
+
+  typedef R(UnboundRunType)(X6, X7, X8);
+
+  static R Run(BindStateBase* base,
+      typename CallbackParamTraits<X6>::ForwardType x6,
+      typename CallbackParamTraits<X7>::ForwardType x7,
+      typename CallbackParamTraits<X8>::ForwardType x8) {
+    StorageType* storage = static_cast<StorageType*>(base);
+
+    // Local references to make debugger stepping easier. If in a debugger,
+    // you really want to warp ahead and step through the
+    // InvokeHelper<>::MakeItSo() call below.
+    typedef typename StorageType::Bound1UnwrapTraits Bound1UnwrapTraits;
+    typedef typename StorageType::Bound2UnwrapTraits Bound2UnwrapTraits;
+    typedef typename StorageType::Bound3UnwrapTraits Bound3UnwrapTraits;
+    typedef typename StorageType::Bound4UnwrapTraits Bound4UnwrapTraits;
+    typedef typename StorageType::Bound5UnwrapTraits Bound5UnwrapTraits;
+
+    typename Bound1UnwrapTraits::ForwardType x1 =
+        Bound1UnwrapTraits::Unwrap(storage->p1_);
+    typename Bound2UnwrapTraits::ForwardType x2 =
+        Bound2UnwrapTraits::Unwrap(storage->p2_);
+    typename Bound3UnwrapTraits::ForwardType x3 =
+        Bound3UnwrapTraits::Unwrap(storage->p3_);
+    typename Bound4UnwrapTraits::ForwardType x4 =
+        Bound4UnwrapTraits::Unwrap(storage->p4_);
+    typename Bound5UnwrapTraits::ForwardType x5 =
+        Bound5UnwrapTraits::Unwrap(storage->p5_);
+    return InvokeHelper<StorageType::IsWeakCall::value, R,
+           typename StorageType::RunnableType,
+           void(typename Bound1UnwrapTraits::ForwardType,
+               typename Bound2UnwrapTraits::ForwardType,
+               typename Bound3UnwrapTraits::ForwardType,
+               typename Bound4UnwrapTraits::ForwardType,
+               typename Bound5UnwrapTraits::ForwardType,
+               typename CallbackParamTraits<X6>::ForwardType x6,
+               typename CallbackParamTraits<X7>::ForwardType x7,
+               typename CallbackParamTraits<X8>::ForwardType x8)>
+               ::MakeItSo(storage->runnable_, CallbackForward(x1),
+                   CallbackForward(x2), CallbackForward(x3),
+                   CallbackForward(x4), CallbackForward(x5),
+                   CallbackForward(x6), CallbackForward(x7),
+                   CallbackForward(x8));
+  }
+};
+
+// Arity 8 -> 2.
+template <typename StorageType, typename R,typename X1, typename X2,
+    typename X3, typename X4, typename X5, typename X6, typename X7,
+    typename X8>
+struct Invoker<6, StorageType, R(X1, X2, X3, X4, X5, X6, X7, X8)> {
+  typedef R(RunType)(BindStateBase*,
+      typename CallbackParamTraits<X7>::ForwardType,
+      typename CallbackParamTraits<X8>::ForwardType);
+
+  typedef R(UnboundRunType)(X7, X8);
+
+  static R Run(BindStateBase* base,
+      typename CallbackParamTraits<X7>::ForwardType x7,
+      typename CallbackParamTraits<X8>::ForwardType x8) {
+    StorageType* storage = static_cast<StorageType*>(base);
+
+    // Local references to make debugger stepping easier. If in a debugger,
+    // you really want to warp ahead and step through the
+    // InvokeHelper<>::MakeItSo() call below.
+    typedef typename StorageType::Bound1UnwrapTraits Bound1UnwrapTraits;
+    typedef typename StorageType::Bound2UnwrapTraits Bound2UnwrapTraits;
+    typedef typename StorageType::Bound3UnwrapTraits Bound3UnwrapTraits;
+    typedef typename StorageType::Bound4UnwrapTraits Bound4UnwrapTraits;
+    typedef typename StorageType::Bound5UnwrapTraits Bound5UnwrapTraits;
+    typedef typename StorageType::Bound6UnwrapTraits Bound6UnwrapTraits;
+
+    typename Bound1UnwrapTraits::ForwardType x1 =
+        Bound1UnwrapTraits::Unwrap(storage->p1_);
+    typename Bound2UnwrapTraits::ForwardType x2 =
+        Bound2UnwrapTraits::Unwrap(storage->p2_);
+    typename Bound3UnwrapTraits::ForwardType x3 =
+        Bound3UnwrapTraits::Unwrap(storage->p3_);
+    typename Bound4UnwrapTraits::ForwardType x4 =
+        Bound4UnwrapTraits::Unwrap(storage->p4_);
+    typename Bound5UnwrapTraits::ForwardType x5 =
+        Bound5UnwrapTraits::Unwrap(storage->p5_);
+    typename Bound6UnwrapTraits::ForwardType x6 =
+        Bound6UnwrapTraits::Unwrap(storage->p6_);
+    return InvokeHelper<StorageType::IsWeakCall::value, R,
+           typename StorageType::RunnableType,
+           void(typename Bound1UnwrapTraits::ForwardType,
+               typename Bound2UnwrapTraits::ForwardType,
+               typename Bound3UnwrapTraits::ForwardType,
+               typename Bound4UnwrapTraits::ForwardType,
+               typename Bound5UnwrapTraits::ForwardType,
+               typename Bound6UnwrapTraits::ForwardType,
+               typename CallbackParamTraits<X7>::ForwardType x7,
+               typename CallbackParamTraits<X8>::ForwardType x8)>
+               ::MakeItSo(storage->runnable_, CallbackForward(x1),
+                   CallbackForward(x2), CallbackForward(x3),
+                   CallbackForward(x4), CallbackForward(x5),
+                   CallbackForward(x6), CallbackForward(x7),
+                   CallbackForward(x8));
+  }
+};
+
+// Arity 8 -> 1.
+template <typename StorageType, typename R,typename X1, typename X2,
+    typename X3, typename X4, typename X5, typename X6, typename X7,
+    typename X8>
+struct Invoker<7, StorageType, R(X1, X2, X3, X4, X5, X6, X7, X8)> {
+  typedef R(RunType)(BindStateBase*,
+      typename CallbackParamTraits<X8>::ForwardType);
+
+  typedef R(UnboundRunType)(X8);
+
+  static R Run(BindStateBase* base,
+      typename CallbackParamTraits<X8>::ForwardType x8) {
+    StorageType* storage = static_cast<StorageType*>(base);
+
+    // Local references to make debugger stepping easier. If in a debugger,
+    // you really want to warp ahead and step through the
+    // InvokeHelper<>::MakeItSo() call below.
+    typedef typename StorageType::Bound1UnwrapTraits Bound1UnwrapTraits;
+    typedef typename StorageType::Bound2UnwrapTraits Bound2UnwrapTraits;
+    typedef typename StorageType::Bound3UnwrapTraits Bound3UnwrapTraits;
+    typedef typename StorageType::Bound4UnwrapTraits Bound4UnwrapTraits;
+    typedef typename StorageType::Bound5UnwrapTraits Bound5UnwrapTraits;
+    typedef typename StorageType::Bound6UnwrapTraits Bound6UnwrapTraits;
+    typedef typename StorageType::Bound7UnwrapTraits Bound7UnwrapTraits;
+
+    typename Bound1UnwrapTraits::ForwardType x1 =
+        Bound1UnwrapTraits::Unwrap(storage->p1_);
+    typename Bound2UnwrapTraits::ForwardType x2 =
+        Bound2UnwrapTraits::Unwrap(storage->p2_);
+    typename Bound3UnwrapTraits::ForwardType x3 =
+        Bound3UnwrapTraits::Unwrap(storage->p3_);
+    typename Bound4UnwrapTraits::ForwardType x4 =
+        Bound4UnwrapTraits::Unwrap(storage->p4_);
+    typename Bound5UnwrapTraits::ForwardType x5 =
+        Bound5UnwrapTraits::Unwrap(storage->p5_);
+    typename Bound6UnwrapTraits::ForwardType x6 =
+        Bound6UnwrapTraits::Unwrap(storage->p6_);
+    typename Bound7UnwrapTraits::ForwardType x7 =
+        Bound7UnwrapTraits::Unwrap(storage->p7_);
+    return InvokeHelper<StorageType::IsWeakCall::value, R,
+           typename StorageType::RunnableType,
+           void(typename Bound1UnwrapTraits::ForwardType,
+               typename Bound2UnwrapTraits::ForwardType,
+               typename Bound3UnwrapTraits::ForwardType,
+               typename Bound4UnwrapTraits::ForwardType,
+               typename Bound5UnwrapTraits::ForwardType,
+               typename Bound6UnwrapTraits::ForwardType,
+               typename Bound7UnwrapTraits::ForwardType,
+               typename CallbackParamTraits<X8>::ForwardType x8)>
+               ::MakeItSo(storage->runnable_, CallbackForward(x1),
+                   CallbackForward(x2), CallbackForward(x3),
+                   CallbackForward(x4), CallbackForward(x5),
+                   CallbackForward(x6), CallbackForward(x7),
+                   CallbackForward(x8));
+  }
+};
+
+// Arity 8 -> 0.
+template <typename StorageType, typename R,typename X1, typename X2,
+    typename X3, typename X4, typename X5, typename X6, typename X7,
+    typename X8>
+struct Invoker<8, StorageType, R(X1, X2, X3, X4, X5, X6, X7, X8)> {
+  typedef R(RunType)(BindStateBase*);
+
+  typedef R(UnboundRunType)();
+
+  static R Run(BindStateBase* base) {
+    StorageType* storage = static_cast<StorageType*>(base);
+
+    // Local references to make debugger stepping easier. If in a debugger,
+    // you really want to warp ahead and step through the
+    // InvokeHelper<>::MakeItSo() call below.
+    typedef typename StorageType::Bound1UnwrapTraits Bound1UnwrapTraits;
+    typedef typename StorageType::Bound2UnwrapTraits Bound2UnwrapTraits;
+    typedef typename StorageType::Bound3UnwrapTraits Bound3UnwrapTraits;
+    typedef typename StorageType::Bound4UnwrapTraits Bound4UnwrapTraits;
+    typedef typename StorageType::Bound5UnwrapTraits Bound5UnwrapTraits;
+    typedef typename StorageType::Bound6UnwrapTraits Bound6UnwrapTraits;
+    typedef typename StorageType::Bound7UnwrapTraits Bound7UnwrapTraits;
+    typedef typename StorageType::Bound8UnwrapTraits Bound8UnwrapTraits;
+
+    typename Bound1UnwrapTraits::ForwardType x1 =
+        Bound1UnwrapTraits::Unwrap(storage->p1_);
+    typename Bound2UnwrapTraits::ForwardType x2 =
+        Bound2UnwrapTraits::Unwrap(storage->p2_);
+    typename Bound3UnwrapTraits::ForwardType x3 =
+        Bound3UnwrapTraits::Unwrap(storage->p3_);
+    typename Bound4UnwrapTraits::ForwardType x4 =
+        Bound4UnwrapTraits::Unwrap(storage->p4_);
+    typename Bound5UnwrapTraits::ForwardType x5 =
+        Bound5UnwrapTraits::Unwrap(storage->p5_);
+    typename Bound6UnwrapTraits::ForwardType x6 =
+        Bound6UnwrapTraits::Unwrap(storage->p6_);
+    typename Bound7UnwrapTraits::ForwardType x7 =
+        Bound7UnwrapTraits::Unwrap(storage->p7_);
+    typename Bound8UnwrapTraits::ForwardType x8 =
+        Bound8UnwrapTraits::Unwrap(storage->p8_);
+    return InvokeHelper<StorageType::IsWeakCall::value, R,
+           typename StorageType::RunnableType,
+           void(typename Bound1UnwrapTraits::ForwardType,
+               typename Bound2UnwrapTraits::ForwardType,
+               typename Bound3UnwrapTraits::ForwardType,
+               typename Bound4UnwrapTraits::ForwardType,
+               typename Bound5UnwrapTraits::ForwardType,
+               typename Bound6UnwrapTraits::ForwardType,
+               typename Bound7UnwrapTraits::ForwardType,
+               typename Bound8UnwrapTraits::ForwardType)>
+               ::MakeItSo(storage->runnable_, CallbackForward(x1),
+                   CallbackForward(x2), CallbackForward(x3),
+                   CallbackForward(x4), CallbackForward(x5),
+                   CallbackForward(x6), CallbackForward(x7),
+                   CallbackForward(x8));
+  }
+};
 
 // BindState<>
 //
@@ -2786,6 +3415,54 @@ struct BindState<Runnable, RunType, void(P1, P2, P3, P4, P5, P6,
   P7 p7_;
 };
 
+template <typename Runnable, typename RunType, typename P1, typename P2,
+    typename P3, typename P4, typename P5, typename P6, typename P7,
+    typename P8>
+struct BindState<Runnable, RunType, void(P1, P2, P3, P4, P5, P6,
+    P7, P8)> : public BindStateBase {
+  typedef Runnable RunnableType;
+  typedef IsWeakMethod<HasIsMethodTag<Runnable>::value, P1> IsWeakCall;
+  typedef Invoker<8, BindState, RunType> InvokerType;
+  typedef typename InvokerType::UnboundRunType UnboundRunType;
+
+  // Convenience typedefs for bound argument types.
+  typedef UnwrapTraits<P1> Bound1UnwrapTraits;
+  typedef UnwrapTraits<P2> Bound2UnwrapTraits;
+  typedef UnwrapTraits<P3> Bound3UnwrapTraits;
+  typedef UnwrapTraits<P4> Bound4UnwrapTraits;
+  typedef UnwrapTraits<P5> Bound5UnwrapTraits;
+  typedef UnwrapTraits<P6> Bound6UnwrapTraits;
+  typedef UnwrapTraits<P7> Bound7UnwrapTraits;
+  typedef UnwrapTraits<P8> Bound8UnwrapTraits;
+
+  BindState(const Runnable& runnable, const P1& p1, const P2& p2, const P3& p3,
+      const P4& p4, const P5& p5, const P6& p6, const P7& p7, const P8& p8)
+      : runnable_(runnable),
+        p1_(p1),
+        p2_(p2),
+        p3_(p3),
+        p4_(p4),
+        p5_(p5),
+        p6_(p6),
+        p7_(p7),
+        p8_(p8) {
+    MaybeRefcount<HasIsMethodTag<Runnable>::value, P1>::AddRef(p1_);
+  }
+
+  virtual ~BindState() {    MaybeRefcount<HasIsMethodTag<Runnable>::value,
+      P1>::Release(p1_);  }
+
+  RunnableType runnable_;
+  P1 p1_;
+  P2 p2_;
+  P3 p3_;
+  P4 p4_;
+  P5 p5_;
+  P6 p6_;
+  P7 p7_;
+  P8 p8_;
+};
+
 }  // namespace internal
 }  // namespace base
 
diff --git a/base/bind_internal_win.h b/base/bind_internal_win.h
index 7a8486a..43e722c 100644
--- a/base/bind_internal_win.h
+++ b/base/bind_internal_win.h
@@ -360,6 +360,33 @@ class RunnableAdapter<R(__fastcall *)(A1, A2, A3, A4, A5, A6, A7)> {
   R (__fastcall *function_)(A1, A2, A3, A4, A5, A6, A7);
 };
 
+// __fastcall Function: Arity 8.
+template <typename R, typename A1, typename A2, typename A3, typename A4,
+    typename A5, typename A6, typename A7, typename A8>
+class RunnableAdapter<R(__fastcall *)(A1, A2, A3, A4, A5, A6, A7, A8)> {
+ public:
+  typedef R (RunType)(A1, A2, A3, A4, A5, A6, A7, A8);
+
+  explicit RunnableAdapter(R(__fastcall *function)(A1, A2, A3, A4, A5, A6, A7,
+                                                   A8))
+      : function_(function) {
+  }
+
+  R Run(typename CallbackParamTraits<A1>::ForwardType a1,
+      typename CallbackParamTraits<A2>::ForwardType a2,
+      typename CallbackParamTraits<A3>::ForwardType a3,
+      typename CallbackParamTraits<A4>::ForwardType a4,
+      typename CallbackParamTraits<A5>::ForwardType a5,
+      typename CallbackParamTraits<A6>::ForwardType a6,
+      typename CallbackParamTraits<A7>::ForwardType a7,
+      typename CallbackParamTraits<A8>::ForwardType a8) {
+    return function_(a1, a2, a3, a4, a5, a6, a7, a8);
+  }
+
+ private:
+  R (__fastcall *function_)(A1, A2, A3, A4, A5, A6, A7, A8);
+};
+
 }  // namespace internal
 }  // namespace base
 
diff --git a/base/callback.h b/base/callback.h
index c613890..430565a 100644
--- a/base/callback.h
+++ b/base/callback.h
@@ -748,6 +748,69 @@ class Callback<R(A1, A2, A3, A4, A5, A6, A7)> : public internal::CallbackBase {
 
 };
 
+template <typename R, typename A1, typename A2, typename A3, typename A4,
+    typename A5, typename A6, typename A7, typename A8>
+class Callback<R(A1, A2, A3, A4, A5, A6, A7, A8)>
+    : public internal::CallbackBase {
+ public:
+  typedef R(RunType)(A1, A2, A3, A4, A5, A6, A7, A8);
+
+  Callback() : CallbackBase(NULL) { }
+
+  // Note that this constructor CANNOT be explicit, and that Bind() CANNOT
+  // return the exact Callback<> type.  See base/bind.h for details.
+  template <typename Runnable, typename BindRunType, typename BoundArgsType>
+  Callback(internal::BindState<Runnable, BindRunType,
+           BoundArgsType>* bind_state)
+      : CallbackBase(bind_state) {
+
+    // Force the assignment to a local variable of PolymorphicInvoke
+    // so the compiler will typecheck that the passed in Run() method has
+    // the correct type.
+    PolymorphicInvoke invoke_func =
+        &internal::BindState<Runnable, BindRunType, BoundArgsType>
+            ::InvokerType::Run;
+    polymorphic_invoke_ = reinterpret_cast<InvokeFuncStorage>(invoke_func);
+  }
+
+  bool Equals(const Callback& other) const {
+    return CallbackBase::Equals(other);
+  }
+
+  R Run(typename internal::CallbackParamTraits<A1>::ForwardType a1,
+        typename internal::CallbackParamTraits<A2>::ForwardType a2,
+        typename internal::CallbackParamTraits<A3>::ForwardType a3,
+        typename internal::CallbackParamTraits<A4>::ForwardType a4,
+        typename internal::CallbackParamTraits<A5>::ForwardType a5,
+        typename internal::CallbackParamTraits<A6>::ForwardType a6,
+        typename internal::CallbackParamTraits<A7>::ForwardType a7,
+        typename internal::CallbackParamTraits<A8>::ForwardType a8) const {
+    PolymorphicInvoke f =
+        reinterpret_cast<PolymorphicInvoke>(polymorphic_invoke_);
+
+    return f(bind_state_.get(), internal::CallbackForward(a1),
+             internal::CallbackForward(a2),
+             internal::CallbackForward(a3),
+             internal::CallbackForward(a4),
+             internal::CallbackForward(a5),
+             internal::CallbackForward(a6),
+             internal::CallbackForward(a7),
+             internal::CallbackForward(a8));
+  }
+
+ private:
+  typedef R(*PolymorphicInvoke)(
+      internal::BindStateBase*,
+          typename internal::CallbackParamTraits<A1>::ForwardType,
+          typename internal::CallbackParamTraits<A2>::ForwardType,
+          typename internal::CallbackParamTraits<A3>::ForwardType,
+          typename internal::CallbackParamTraits<A4>::ForwardType,
+          typename internal::CallbackParamTraits<A5>::ForwardType,
+          typename internal::CallbackParamTraits<A6>::ForwardType,
+          typename internal::CallbackParamTraits<A7>::ForwardType,
+          typename internal::CallbackParamTraits<A8>::ForwardType);
+
+};
 
 // Syntactic sugar to make Callbacks<void(void)> easier to declare since it
 // will be used in a lot of APIs with delayed execution.