[keys] propagate PropertyFilter to proxy targets in KeyAccumulator

test/mjsunit/regress/regress-5174.js

Index: test/mjsunit/regress/regress-5174.js
diff --git a/test/mjsunit/regress/regress-5174.js b/test/mjsunit/regress/regress-5174.js
new file mode 100644
index 0000000000000000000000000000000000000000..390d24e68210af8fa2d28c0675a619ddc03dc12e
--- /dev/null
+++ b/test/mjsunit/regress/regress-5174.js
@@ -0,0 +1,6 @@
+// Copyright 2016 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.
+
+assertEquals([], Object.keys(new Proxy([], {})));
+assertEquals([], Object.keys(new Proxy(/regex/, {})));