[proxies] allow duplicate keys for [[OwnPropertyKeys]] trap.

test/mjsunit/harmony/proxies-ownkeys.js

Index: test/mjsunit/harmony/proxies-ownkeys.js
diff --git a/test/mjsunit/harmony/proxies-ownkeys.js b/test/mjsunit/harmony/proxies-ownkeys.js
index 6a7ae64d78b9602cf8bf579578ba4d98b46b4f6b..88350cca02d40c662fe5966ca287c202390114ef 100644
--- a/test/mjsunit/harmony/proxies-ownkeys.js
+++ b/test/mjsunit/harmony/proxies-ownkeys.js
@@ -56,6 +56,10 @@ assertEquals(["a", "b", "c"], Reflect.ownKeys(proxy));
 keys.length = Math.pow(2, 33);
 assertThrows("Reflect.ownKeys(proxy)", RangeError);
 
+// Check that we allow duplicated keys.
+keys  = ['a', 'a', 'a']
+assertEquals(keys, Reflect.ownKeys(proxy));
+
 // Non-Name results throw.
 keys = [1];
 assertThrows("Reflect.ownKeys(proxy)", TypeError);
@@ -73,6 +77,10 @@ assertThrows("Reflect.ownKeys(proxy)", TypeError);
 keys = ["nonconf"];
 assertEquals(keys, Reflect.ownKeys(proxy));
 
+// Check that we allow duplicated keys.
+keys  = ['nonconf', 'nonconf', 'nonconf']
+assertEquals(keys, Reflect.ownKeys(proxy));
+
 // Step 19a: The trap result must all keys of a non-extensible target.
 Object.preventExtensions(target);
 assertThrows("Reflect.ownKeys(proxy)", TypeError);
@@ -82,3 +90,7 @@ assertEquals(keys, Reflect.ownKeys(proxy));
 // Step 20: The trap result must not add keys to a non-extensible target.
 keys = ["nonconf", "target_one", "fantasy"];
 assertThrows("Reflect.ownKeys(proxy)", TypeError);
+
+// Check that we allow duplicated keys.
+keys  = ['nonconf', 'target_one', 'nonconf', 'nonconf', 'target_one',]
+assertEquals(keys, Reflect.ownKeys(proxy));