[async-functions] support await expressions in finally statements

src/utils.h

Index: src/utils.h
diff --git a/src/utils.h b/src/utils.h
index 6d0d3c84a3845750283340bf2bf611576f460994..7f5cf19fc70608442df9cd5253aac34ad6a2a288 100644
--- a/src/utils.h
+++ b/src/utils.h
@@ -1707,6 +1707,25 @@ class ThreadedListZoneEntry final : public ZoneObject {
   DISALLOW_COPY_AND_ASSIGN(ThreadedListZoneEntry);
 };
 
+template <typename T>
+class ScopedAssignment {
+ public:
+  V8_INLINE ScopedAssignment(T& previous, T&& value)
+      : location_(&previous), prev_(previous) {
+    *location_ = value;
+  }
+  V8_INLINE ScopedAssignment(T& previous, const T& value)
+      : location_(&previous), prev_(previous) {
+    *location_ = value;
+  }
+
+  V8_INLINE ~ScopedAssignment() { *location_ = prev_; }
+
+ private:
+  T* location_;
+  T prev_;
+};
+
 }  // namespace internal
 }  // namespace v8