Add object spread test

test/language/expressions/object/object-spread-proxy-ownkeys-returned-keys-order.js

@@ -0,0 +1,45 @@
+// Copyright (C) 2020 Alexey Shvayka. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+/*---
+esid: sec-object-initializer-runtime-semantics-propertydefinitionevaluation
+description: >
+  Proxy keys are iterated in order they were provided by "ownKeys" trap.
+info: |
+  PropertyDefinition : ... AssignmentExpression
+
+  [...]
+  4. Return ? CopyDataProperties(object, fromValue, excludedNames).
+
+  CopyDataProperties ( target, source, excludedItems )
+
+  [...]
+  5. Let keys be ? from.[[OwnPropertyKeys]]().
+  6. For each element nextKey of keys in List order, do
+    [...]
+    c. If excluded is false, then
+      i. Let desc be ? from.[[GetOwnProperty]](nextKey).
+
+  [[OwnPropertyKeys]] ( )
+
+  [...]
+  7. Let trapResultArray be ? Call(trap, handler, « target »).
+  8. Let trapResult be ? CreateListFromArrayLike(trapResultArray, « String, Symbol »).
+  [...]
+  23. Return trapResult.
+features: [object-spread, Proxy, Symbol]
+includes: [compareArray.js]
+---*/
+
+var getOwnKeys = [];
+var ownKeysResult = [Symbol(), "foo", "0"];
+var proxy = new Proxy({}, {
+  getOwnPropertyDescriptor: function(_target, key) {
+    getOwnKeys.push(key);
+  },
+  ownKeys: function() {
+    return ownKeysResult;
+  },
+});
+
+({...proxy});
+assert.compareArray(getOwnKeys, ownKeysResult);