[async-iteration] expose Symbol.asyncIterator behind flag --harmony-async-iteration

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/base/ieee754.h"
 #include "src/code-stubs.h"
@@ skipping 3574 matching lines @@
 
   Handle<Object> unscopables =
       JSObject::GetProperty(array_prototype, factory()->unscopables_symbol())
           .ToHandleChecked();
   DCHECK(unscopables->IsJSObject());
   JSObject::AddProperty(Handle<JSObject>::cast(unscopables),
                         factory()->values_string(), factory()->true_value(),
                         NONE);
 }
 
+void Genesis::InitializeGlobal_harmony_async_iteration() {
+  if (!FLAG_harmony_async_iteration) return;
+  Handle<JSFunction> symbol_fun(native_context()->symbol_function());
+  InstallConstant(isolate(), symbol_fun, "asyncIterator",
+                  factory()->async_iterator_symbol());
+}
+
 Handle<JSFunction> Genesis::InstallArrayBuffer(Handle<JSObject> target,
                                                const char* name,
                                                Builtins::Name call,
                                                BuiltinFunctionId id) {
   // Create the %ArrayBufferPrototype%
   // Setup the {prototype} with the given {name} for @@toStringTag.
   Handle<JSObject> prototype =
       factory()->NewJSObject(isolate()->object_function(), TENURED);
   JSObject::AddProperty(prototype, factory()->to_string_tag_symbol(),
                         factory()->NewStringFromAsciiChecked(name),
@@ skipping 445 matching lines @@
 #ifdef V8_I18N_SUPPORT
   static const char* icu_case_mapping_natives[] = {"native icu-case-mapping.js",
                                                    nullptr};
   static const char* datetime_format_to_parts_natives[] = {
       "native datetime-format-to-parts.js", nullptr};
 #endif
   static const char* harmony_restrictive_generators_natives[] = {nullptr};
   static const char* harmony_trailing_commas_natives[] = {nullptr};
   static const char* harmony_class_fields_natives[] = {nullptr};
   static const char* harmony_object_rest_spread_natives[] = {nullptr};
+  static const char* harmony_async_iteration_natives[] = {nullptr};
 
   for (int i = ExperimentalNatives::GetDebuggerCount();
        i < ExperimentalNatives::GetBuiltinsCount(); i++) {
 #define INSTALL_EXPERIMENTAL_NATIVES(id, desc)                                \
   if (FLAG_##id) {                                                            \
     for (size_t j = 0; id##_natives[j] != NULL; j++) {                        \
       Vector<const char> script_name = ExperimentalNatives::GetScriptName(i); \
       if (strncmp(script_name.start(), id##_natives[j],                       \
                   script_name.length()) == 0) {                               \
         if (!Bootstrapper::CompileExperimentalBuiltin(isolate(), i)) {        \
@@ skipping 746 matching lines @@
 }
 
 
 // Called when the top-level V8 mutex is destroyed.
 void Bootstrapper::FreeThreadResources() {
   DCHECK(!IsActive());
 }
 
 }  // namespace internal
 }  // namespace v8