[runtime] Fix effect of setting .prototype on generator functions.

src/bootstrapper.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/bootstrapper.h"
 
 #include "src/accessors.h"
 #include "src/api-natives.h"
 #include "src/code-stubs.h"
 #include "src/extensions/externalize-string-extension.h"
@@ skipping 731 matching lines @@
   strict_function_map_writable_prototype_ =
       CreateStrictFunctionMap(FUNCTION_WITH_WRITEABLE_PROTOTYPE, empty);
 }
 
 void Genesis::CreateIteratorMaps(Handle<JSFunction> empty) {
   // Create iterator-related meta-objects.
   Handle<JSObject> iterator_prototype =
       factory()->NewJSObject(isolate()->object_function(), TENURED);
   Handle<JSObject> generator_object_prototype =
       factory()->NewJSObject(isolate()->object_function(), TENURED);
+  native_context()->set_initial_generator_prototype(
+      *generator_object_prototype);
   SetObjectPrototype(generator_object_prototype, iterator_prototype);
   Handle<JSObject> generator_function_prototype =
       factory()->NewJSObject(isolate()->object_function(), TENURED);
   SetObjectPrototype(generator_function_prototype, empty);
 
   JSObject::AddProperty(
       generator_function_prototype, factory()->to_string_tag_symbol(),
       factory()->NewStringFromAsciiChecked("GeneratorFunction"),
       static_cast<PropertyAttributes>(DONT_ENUM | READ_ONLY));
   JSObject::AddProperty(generator_function_prototype,
@@ skipping 3005 matching lines @@
 }
 
 
 // Called when the top-level V8 mutex is destroyed.
 void Bootstrapper::FreeThreadResources() {
   DCHECK(!IsActive());
 }
 
 }  // namespace internal
 }  // namespace v8