diff --git a/base/synchronization/cancellation_flag.cc b/base/synchronization/cancellation_flag.cc
index ad3b551..ca5c0a8 100644
--- a/base/synchronization/cancellation_flag.cc
+++ b/base/synchronization/cancellation_flag.cc
@@ -19,4 +19,8 @@
   return base::subtle::Acquire_Load(&flag_) != 0;
 }
 
+void CancellationFlag::UnsafeResetForTesting() {
+  base::subtle::Release_Store(&flag_, 0);
+}
+
 }  // namespace base