Make generators non-constructable.

src/runtime/runtime-generator.cc

 // Copyright 2014 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.
 
 #include "src/runtime/runtime-utils.h"
 
 #include "src/arguments.h"
 #include "src/factory.h"
 #include "src/frames-inl.h"
 #include "src/objects-inl.h"
 
 namespace v8 {
 namespace internal {
 
 RUNTIME_FUNCTION(Runtime_CreateJSGeneratorObject) {
   HandleScope scope(isolate);
   DCHECK(args.length() == 0);
 
   JavaScriptFrameIterator it(isolate);
   JavaScriptFrame* frame = it.frame();
   Handle<JSFunction> function(frame->function());
   RUNTIME_ASSERT(function->shared()->is_generator());
 
   Handle<JSGeneratorObject> generator;
-  if (frame->IsConstructor()) {
-    generator = handle(JSGeneratorObject::cast(frame->receiver()));
-  } else {
-    generator = isolate->factory()->NewJSGeneratorObject(function);
-  }
+  DCHECK(!frame->IsConstructor());
+  generator = isolate->factory()->NewJSGeneratorObject(function);
   generator->set_function(*function);
   generator->set_context(Context::cast(frame->context()));
   generator->set_receiver(frame->receiver());
   generator->set_continuation(0);
   generator->set_operand_stack(isolate->heap()->empty_fixed_array());
 
   return *generator;
 }
 
 
@@ skipping 174 matching lines @@
   return NULL;
 }
 
 
 RUNTIME_FUNCTION(Runtime_GeneratorThrow) {
   UNREACHABLE();  // Optimization disabled in SetUpGenerators().
   return NULL;
 }
 }  // namespace internal
 }  // namespace v8