fixup! Add tests for MethodDefinition forms new to ES6

Avoid extending builtin prototype and consistently define a shadowing
property on the object instance to help recognize a possible
implementation bug.

test/language/expressions/object/method-definition/generator-super-prop-body.js

@@ -10,18 +10,14 @@ author: Sam Mikes
 description: GeneratorMethod body uses SuperProperty (allowed)
 ---*/
 
-var value = {};
 var obj;
 
-try {
-  Object.prototype.Test262Attr = value;
-  obj = {
-    *foo() {
-      return super.Test262Attr;
-    }
-  };
+var obj = {
+  *foo() {
+    return super.toString;
+  }
+};
 
-  assert.sameValue(obj.foo().next().value, value);
-} finally {
-  delete Object.prototype.Test262Attr;
-}
+obj.toString = null;
+
+assert.sameValue(obj.foo().next().value, Object.prototype.toString);

test/language/expressions/object/method-definition/generator-super-prop-param.js

@@ -11,18 +11,12 @@ description: GeneratorMethod uses SuperProperty (allowed)
 features: [ default-arg, generator, super ]
 ---*/
 
-var value = {};
-var obj;
+var obj = {
+  *foo(a = super.toString) {
+    return a;
+  }
+};
 
-try {
-  Object.prototype.Test262Attr = value;
-  obj = {
-    *foo(a = super.Test262Attr) {
-      return a;
-    }
-  };
+obj.toString = null;
 
-  assert.sameValue(obj.foo().next().value, value);
-} finally {
-  delete Object.prototype.Test262Attr;
-}
+assert.sameValue(obj.foo().next().value, Object.prototype.toString);

test/language/expressions/object/method-definition/name-super-prop-body.js

@@ -8,18 +8,12 @@ es6id: 14.3.8
 features: [super]
 ---*/
 
-var value = {};
-var obj;
+var obj = {
+  method() {
+    return super.toString;
+  }
+};
 
-try {
-  Object.prototype.Test262Attr = value;
-  obj = {
-    Test262Attr: null,
-    method() {
-      return super.Test262Attr;
-    }
-  };
-  assert.sameValue(obj.method(), value);
-} finally {
-  delete Object.prototype.Test262Attr;
-}
+obj.toString = null;
+
+assert.sameValue(obj.method(), Object.prototype.toString);

test/language/expressions/object/method-definition/name-super-prop-param.js

@@ -8,19 +8,12 @@ es6id: 14.3.8
 features: [super]
 ---*/
 
-var value = {};
-var obj;
+var obj = {
+  method(x = super.toString) {
+    return x;
+  }
+};
 
-try {
-  Object.prototype.Test262Attr = value;
-  obj = {
-    Test262Attr: null,
-    method(x = super.Test262Attr) {
-      return x;
-    }
-  };
+obj.toString = null;
 
-  assert.sameValue(obj.method(), value);
-} finally {
-  delete Object.prototype.Test262Attr;
-}
+assert.sameValue(obj.method(), Object.prototype.toString);