Make JSProxies always be in slow mode

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 2431 matching lines @@
   // Next to the default proxy, we need maps indicating callable and
   // constructable proxies.
 
   Handle<Map> proxy_function_map =
       Map::Copy(isolate()->sloppy_function_without_prototype_map(), "Proxy");
   proxy_function_map->set_is_constructor();
   native_context()->set_proxy_function_map(*proxy_function_map);
 
   Handle<Map> proxy_map =
       factory()->NewMap(JS_PROXY_TYPE, JSProxy::kSize, FAST_ELEMENTS);
+  proxy_map->set_dictionary_map(true);
   native_context()->set_proxy_map(*proxy_map);
 
   Handle<Map> proxy_callable_map = Map::Copy(proxy_map, "callable Proxy");
   proxy_callable_map->set_is_callable();
   native_context()->set_proxy_callable_map(*proxy_callable_map);
   proxy_callable_map->SetConstructor(native_context()->function_function());
 
   Handle<Map> proxy_constructor_map =
       Map::Copy(proxy_callable_map, "constructor Proxy");
   proxy_constructor_map->set_is_constructor();
@@ skipping 1048 matching lines @@
 }
 
 
 // Called when the top-level V8 mutex is destroyed.
 void Bootstrapper::FreeThreadResources() {
   DCHECK(!IsActive());
 }
 
 }  // namespace internal
 }  // namespace v8