[async-functions] support await expressions in finally statements

src/utils.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_UTILS_H_
 #define V8_UTILS_H_
 
 #include <limits.h>
 #include <stdlib.h>
 #include <string.h>
@@ skipping 1689 matching lines @@
 
   T value() { return value_; }
   ThreadedListZoneEntry<T>** next() { return &next_; }
 
  private:
   T value_;
   ThreadedListZoneEntry<T>* next_;
   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
 
 #endif  // V8_UTILS_H_