Add failing test for issue 186:

    http://code.google.com/p/v8/issues/detail?id=186

The issue is that the extension object is a normal javascript object
on which assignments to __proto__ changes the prototype chain.
Review URL: http://codereview.chromium.org/18221

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@1069 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

test/mjsunit/bugs/bug-186.js

+// Copyright 2009 the V8 project authors. All rights reserved.
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+//       notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+//       copyright notice, this list of conditions and the following
+//       disclaimer in the documentation and/or other materials provided
+//       with the distribution.
+//     * Neither the name of Google Inc. nor the names of its
+//       contributors may be used to endorse or promote products derived
+//       from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Make sure that eval can introduce a local variable called __proto__.
+// See http://code.google.com/p/v8/issues/detail?id=186
+
+var setterCalled = false;
+
+var o = {};
+o.__defineSetter__("x", function() { setterCalled = true; });
+
+function testLocal() {
+  // Add property called __proto__ to the extension object.
+  eval("var __proto__ = o");
+  // Check that the extension object's prototype did not change.
+  eval("var x = 27");
+  assertFalse(setterCalled, "prototype of extension object changed");
+}
+
+function testGlobal() {
+  // Assign to the global __proto__ property.
+  eval("__proto__ = o");
+  // Check that the prototype of the global object changed.
+  eval("x = 27");
+  assertTrue(setterCalled, "prototype of global object did not change");
+  setterCalled = false;
+}
+
+testLocal();
+testGlobal();
+