[runtime] [proxies] adding tests for uncovered branches

test/mjsunit/harmony/proxies-define-property.js

 // Copyright 2015 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: --harmony-proxies
 
 // Check basic call to trap.
 
 var g_target, g_name, g_desc;
 var handler = {
   defineProperty: function(target, name, desc) {
     g_target = target;
     g_name = name;
     g_desc = desc;
     return true;
   }
 }
 var target = {}
 var proxy = new Proxy(target, handler);
 var desc = { value: 1, writable: true, configurable: true, enumerable: true };
 Object.defineProperty(proxy, "foo", desc);
 assertSame(target, g_target);
 assertEquals("foo", g_name);
 assertEquals(desc, g_desc);
 
-// Check specific steps in the spec:
+// Check specific steps in the spec
+
+// Step 4: revoked handler
+var pair = Proxy.revocable(target, handler);
+Object.defineProperty(proxy, "foo2", desc);
+assertSame(target, g_target);
+assertEquals("foo2", g_name);
+assertEquals(desc, g_desc);
+pair.revoke();
+assertThrows('Object.defineProperty(pair.proxy, "bar", desc);', TypeError);
 
 // Step 6: Trap isn't callable.
 handler.defineProperty = 1;
 assertThrows("Object.defineProperty(proxy, 'foo', {value: 2})", TypeError);
 
 // Step 7: Trap is undefined.
 handler.defineProperty = undefined;
 Object.defineProperty(proxy, "prop1", desc);
 assertEquals(desc, Object.getOwnPropertyDescriptor(target, "prop1"));
 var target2 = {};
@@ skipping 29 matching lines @@
 // Step 16a: Trap returns true for non-compatible property descriptor.
 Object.defineProperty(target, "foo",
                       {value: 1, writable: false, configurable: false});
 assertThrows("Object.defineProperty(proxy, 'foo', {value: 2})", TypeError);
 
 // Step 16b: Trap returns true for overwriting a configurable property
 // with a non-configurable descriptor.
 target.bar = "baz";
 assertThrows("Object.defineProperty(proxy, 'bar', {configurable: false})",
              TypeError);