[ic] Don't check full prototype chain if name is a private symbol.

test/mjsunit/regress/regress-crbug-664974.js

Index: test/mjsunit/regress/regress-crbug-664974.js
diff --git a/test/mjsunit/regress/regress-crbug-664974.js b/test/mjsunit/regress/regress-crbug-664974.js
new file mode 100644
index 0000000000000000000000000000000000000000..37ad4f9dc24e11f46931c2e7ed9525b95fecde4a
--- /dev/null
+++ b/test/mjsunit/regress/regress-crbug-664974.js
@@ -0,0 +1,13 @@
+// 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.
+
+for (var i = 0; i < 2000; i++) {
+  Object.prototype['X'+i] = true;
+}
+
+var m = new Map();
+m.set(Object.prototype, 23);
+
+var o = {};
+m.set(o, 42);