sdk/lib/_internal/js_runtime/lib/preambles/seal_native_object.js - sdk - Git at Google

 // Copyright (c) 2023, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.

 // The native JavaScript Object prototype is sealed before loading the Dart
 // program to guard against prototype pollution.
 delete Object.prototype.__proto__;
 Object.seal(Object.prototype);
	// Copyright (c) 2023, the Dart project authors. Please see the AUTHORS file
	// for details. All rights reserved. Use of this source code is governed by a
	// BSD-style license that can be found in the LICENSE file.

	// The native JavaScript Object prototype is sealed before loading the Dart
	// program to guard against prototype pollution.
	delete Object.prototype.__proto__;
	Object.seal(Object.prototype);