Add Callback::IsCancelled

base/bind_internal.h

Index: base/bind_internal.h
diff --git a/base/bind_internal.h b/base/bind_internal.h
index 0c7c8abda227de1cb2b29c2ab211106c20a5a8c9..98a73908375394b8e03b70eea60b40741aba4b0d 100644
--- a/base/bind_internal.h
+++ b/base/bind_internal.h
@@ -373,6 +373,38 @@ IsNull(const Functor&) {
   return false;
 }
 
+template <typename Functor, typename... BoundArgs>
+struct BindState;
+
+template <typename BindStateType, typename SFINAE = void>
+struct CancellationChecker {
+  static bool Run(const BindStateBase*) {
+    return false;
+  }
+};
+
+template <typename Functor, typename... BoundArgs>
+struct CancellationChecker<
+    BindState<Functor, BoundArgs...>,
+    typename std::enable_if<IsWeakMethod<FunctorTraits<Functor>::is_method,
+                                         BoundArgs...>::value>::type> {
+  static bool Run(const BindStateBase* base) {
+    using BindStateType = BindState<Functor, BoundArgs...>;
+    const BindStateType* bind_state = static_cast<const BindStateType*>(base);
+    return !base::get<0>(bind_state->bound_args_);
+  }
+};
+
+template <typename Signature, typename... BoundArgs>
+struct CancellationChecker<BindState<Callback<Signature>, BoundArgs...>> {
+  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();
+  }
+};
+
 // BindState<>
 //
 // This stores all the state passed into Bind().
@@ -382,7 +414,8 @@ struct BindState final : BindStateBase {
   explicit BindState(BindStateBase::InvokeFuncStorage invoke_func,
                      ForwardFunctor&& functor,
                      ForwardBoundArgs&&... bound_args)
-      : BindStateBase(invoke_func, &Destroy),
+      : BindStateBase(invoke_func, &Destroy,
+                      &CancellationChecker<BindState>::Run),
         functor_(std::forward<ForwardFunctor>(functor)),
         bound_args_(std::forward<ForwardBoundArgs>(bound_args)...) {
     DCHECK(!IsNull(functor_));