Make generators non-constructable.

test/mjsunit/es6/generators-iteration.js

 // Copyright 2013 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
@@ skipping 83 matching lines @@
 
   testNext(g);
   testSend(g);
   testThrow(g);
 
   testNext(function*() { return yield* g(); });
   testSend(function*() { return yield* g(); });
   testThrow(function*() { return yield* g(); });
 
   if (g instanceof GeneratorFunction) {
-    testNext(function() { return new g(); });
-    testSend(function() { return new g(); });
-    testThrow(function() { return new g(); });
+    testNext(g);
+    testSend(g);
+    testThrow(g);
   }
 }
 
 TestGenerator(function* g1() { },
               [undefined],
               "foo",
               [undefined]);
 
 TestGenerator(function* g2() { yield 1; },
               [1, undefined],
@@ skipping 135 matching lines @@
     function g17() {
       function* g() { yield this.x; yield this.y; }
       var o = { start: g, x: 1, y: 2 };
       return o.start();
     },
     [1, 2, undefined],
     "foo",
     [1, 2, undefined]);
 
 TestGenerator(
-    function g18() {
-      function* g() { yield this.x; yield this.y; }
-      var iter = new g;
-      iter.x = 1;
-      iter.y = 2;
-      return iter;
-    },
-    [1, 2, undefined],
-    "foo",
-    [1, 2, undefined]);
-
-TestGenerator(
     function* g19() {
       var x = 1;
       yield x;
       with({x:2}) { yield x; }
       yield x;
     },
     [1, 2, 1, undefined],
     "foo",
     [1, 2, 1, undefined]);
 
@@ skipping 402 matching lines @@
   function TestThrowRecursion() {
     function* g() { yield iter.throw(1); }
     var iter = g();
     return iter.next();
   }
   assertThrows(TestNextRecursion, Error);
   assertThrows(TestSendRecursion, Error);
   assertThrows(TestThrowRecursion, Error);
 }
 TestRecursion();