Expose base::Callback::IsCancelled via WTF::Function

third_party/WebKit/Source/wtf/Functional.h

Index: third_party/WebKit/Source/wtf/Functional.h
diff --git a/third_party/WebKit/Source/wtf/Functional.h b/third_party/WebKit/Source/wtf/Functional.h
index 97d156086f32ca4bcd6157581821fc1431e82daf..d081c8beed52307a49c6c452e2fee2bfb806ea8d 100644
--- a/third_party/WebKit/Source/wtf/Functional.h
+++ b/third_party/WebKit/Source/wtf/Functional.h
@@ -204,6 +204,11 @@ public:
         return m_callback.Run(std::forward<Args>(args)...);
     }
 
+    bool isCancelled() const
+    {
+        return m_callback.IsCancelled();
+    }
+
     friend base::Callback<R(Args...)> convertToBaseCallback(std::unique_ptr<Function> function)
     {
         return std::move(function->m_callback);