Add "own" symbols support.

test/mjsunit/own-symbols.js

+// Copyright 2014 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.
+//
+// Flags: --allow-natives-syntax
+
+var s = %CreatePrivateOwnSymbol("s");
+var s1 = %CreatePrivateOwnSymbol("s1");
+
+function TestSimple() {
+  var p = {}
+  p[s] = "moo";
+
+  var o = Object.create(p);
+
+  assertEquals(undefined, o[s]);
+  assertEquals("moo", p[s]);
+
+  o[s] = "bow-wow";
+  assertEquals("bow-wow", o[s]);
+  assertEquals("moo", p[s]);
+}
+
+TestSimple();
+
+
+function TestICs() {
+  var p = {}
+  p[s] = "moo";
+
+
+  var o = Object.create(p);
+  o[s1] = "bow-wow";
+  function checkNonOwn(o) {
+    assertEquals(undefined, o[s]);
+    assertEquals("bow-wow", o[s1]);
+  }
+
+  checkNonOwn(o);
+
+  // Test monomorphic/optimized.
+  for (var i = 0; i < 1000; i++) {
+    checkNonOwn(o);
+  }
+
+  // Test non-monomorphic.
+  for (var i = 0; i < 1000; i++) {
+    var oNew = Object.create(p);
+    oNew["s" + i] = i;
+    oNew[s1] = "bow-wow";
+    checkNonOwn(oNew);
+  }
+}
+
+TestICs();