Support nested OnceCallback on Callback::IsCancelled

base/bind_internal.h

Index: base/bind_internal.h
diff --git a/base/bind_internal.h b/base/bind_internal.h
index 5845a4d031de9c3df658820a4b2f4cc3e545fe61..0872240e4562a7b44cdc7c8aa064852d08f14258 100644
--- a/base/bind_internal.h
+++ b/base/bind_internal.h
@@ -411,17 +411,25 @@ struct CancellationChecker<
   }
 };
 
-template <typename Signature, typename... BoundArgs>
-struct CancellationChecker<BindState<Callback<Signature>, BoundArgs...>> {
+template <typename BindStateType>
+struct CallbackCancellationChecker {
   static constexpr bool is_cancellable = true;
   static bool Run(const BindStateBase* base) {
-    using Functor = Callback<Signature>;
-    using BindStateType = BindState<Functor, BoundArgs...>;
-    const BindStateType* bind_state = static_cast<const BindStateType*>(base);
-    return bind_state->functor_.IsCancelled();
+    return static_cast<const BindStateType*>(base)->functor_.IsCancelled();
   }
 };
 
+template <typename Signature, typename... BoundArgs>
+struct CancellationChecker<BindState<OnceCallback<Signature>, BoundArgs...>>
+    : CallbackCancellationChecker<
+          BindState<OnceCallback<Signature>, BoundArgs...>> {};
+
+template <typename Signature, typename... BoundArgs>
+struct CancellationChecker<
+    BindState<RepeatingCallback<Signature>, BoundArgs...>>
+    : CallbackCancellationChecker<
+          BindState<RepeatingCallback<Signature>, BoundArgs...>> {};
+
 // BindState<>
 //
 // This stores all the state passed into Bind().