Add tests for IdentifierReference as property

From the ES6 specification:

> ## PropertyDefinition : IdentifierReference
>
> 1. Let propName be StringValue of IdentifierReference.
> 2. Let exprValue be the result of evaluating IdentifierReference.
> 3. ReturnIfAbrupt(exprValue).
> 4. Let propValue be GetValue(exprValue).
> 5. ReturnIfAbrupt(propValue).
> 6. Assert: enumerable is true.
> 7. Return CreateDataPropertyOrThrow(object, propName, propValue).

test/language/expressions/object/prop-def-id-eval-error-2.js

@@ -0,0 +1,22 @@
+// Copyright (C) Copyright 2015 the V8 project authors. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+/*---
+es6id: 12.2.5.9
+description: >
+    Errors thrown during IdentifierReference evaluation are forwarded to the
+    runtime.
+flags: [noStrict]
+features: [Proxy]
+---*/
+
+var p = new Proxy({}, {
+  has: function () {
+    throw new Test262Error();
+  }
+});
+
+assert.throws(Test262Error, function() {
+  with (p) {
+    ({attr});
+  }
+});

test/language/expressions/object/prop-def-id-eval-error.js

@@ -0,0 +1,21 @@
+// Copyright (C) Copyright 2015 the V8 project authors. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+/*---
+es6id: 12.2.5.9
+description: >
+    Errors thrown during IdentifierReference evaluation are forwarded to the
+    runtime.
+flags: [noStrict]
+features: [Symbol, Symbol.unscopables]
+---*/
+
+var obj = {
+  attr: null,
+  get [Symbol.unscopables]() { throw new Test262Error(); }
+};
+
+assert.throws(Test262Error, function() {
+  with (obj) {
+    ({ attr });
+  }
+});

test/language/expressions/object/prop-def-id-get-error.js

@@ -0,0 +1,12 @@
+// Copyright (C) Copyright 2015 the V8 project authors. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+/*---
+es6id: 12.2.5.9
+description: >
+    Errors thrown during IdentifierReference value retrieval are forwarded to
+    the runtime.
+---*/
+
+assert.throws(ReferenceError, function() {
+  ({ unresolvable });
+});

test/language/expressions/object/prop-def-id-valid.js

@@ -0,0 +1,21 @@
+// Copyright (C) Copyright 2015 the V8 project authors. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+/*---
+es6id: 12.2.5.9
+description: >
+    When a valid IdentifierReference appears in an object initializer, a new
+    data property is created. The property name is the string value of the
+    identifier, the property value is the value of the identifier, and the
+    property is enumerable, writable, and configurable.
+includes: [propertyHelper.js]
+---*/
+
+var attr = 23;
+var obj;
+
+obj = { attr };
+
+assert.sameValue(obj.attr, 23);
+verifyEnumerable(obj, 'attr');
+verifyWritable(obj, 'attr');
+verifyConfigurable(obj, 'attr');