[es6] Fix Function and GeneratorFunction built-ins subclassing.

test/mjsunit/regress/regress-function-constructor-receiver.js

Index: test/mjsunit/regress/regress-function-constructor-receiver.js
diff --git a/test/mjsunit/regress/regress-function-constructor-receiver.js b/test/mjsunit/regress/regress-function-constructor-receiver.js
index f345435ade0d72063307bf49267e9f11513ce42d..5d713803bef1ff93e99f20fd0510933df43a826f 100644
--- a/test/mjsunit/regress/regress-function-constructor-receiver.js
+++ b/test/mjsunit/regress/regress-function-constructor-receiver.js
@@ -10,8 +10,8 @@ try {
   new Function({toString:0,valueOf:0});
 } catch (e) {
   threw = true;
-  // Ensure that the receiver during "new Function" is the global proxy.
-  assertEquals(this, e.stack[0].getThis());
+  // Ensure that the receiver during "new Function" is the undefined value.
+  assertEquals(undefined, e.stack[0].getThis());
 }
 
 assertTrue(threw);