Go to slow path when JSON.stringifying the global proxy.

src/json-stringifier.h

 // Copyright 2012 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.
 
 #ifndef V8_JSON_STRINGIFIER_H_
 #define V8_JSON_STRINGIFIER_H_
 
 #include "src/v8.h"
 
 #include "src/conversions.h"
@@ skipping 424 matching lines @@
       if (deferred_string_key) SerializeDeferredKey(comma, key);
       return SerializeJSValue(Handle<JSValue>::cast(object));
     case JS_FUNCTION_TYPE:
       return UNCHANGED;
     default:
       if (object->IsString()) {
         if (deferred_string_key) SerializeDeferredKey(comma, key);
         SerializeString(Handle<String>::cast(object));
         return SUCCESS;
       } else if (object->IsJSObject()) {
-        if (object->IsAccessCheckNeeded()) break;
+        // Go to slow path for global proxy and objects requiring access checks.
+        if (object->IsAccessCheckNeeded() || object->IsJSGlobalProxy()) break;
         if (deferred_string_key) SerializeDeferredKey(comma, key);
         return SerializeJSObject(Handle<JSObject>::cast(object));
       }
   }
 
   return SerializeGeneric(object, key, comma, deferred_string_key);
 }
 
 
 BasicJsonStringifier::Result BasicJsonStringifier::SerializeGeneric(
@@ skipping 167 matching lines @@
   }
   return SUCCESS;
 }
 
 
 BasicJsonStringifier::Result BasicJsonStringifier::SerializeJSObject(
     Handle<JSObject> object) {
   HandleScope handle_scope(isolate_);
   Result stack_push = StackPush(object);
   if (stack_push != SUCCESS) return stack_push;
-  if (object->IsJSGlobalProxy()) {
-    object = Handle<JSObject>(
-                 JSObject::cast(object->GetPrototype()), isolate_);
-    ASSERT(object->IsGlobalObject());
-  }
+  ASSERT(!object->IsJSGlobalProxy() && !object->IsGlobalObject());
 
   Append('{');
   bool comma = false;
 
   if (object->HasFastProperties() &&
       !object->HasIndexedInterceptor() &&
       !object->HasNamedInterceptor() &&
       object->elements()->length() == 0) {
     Handle<Map> map(object->map());
     for (int i = 0; i < map->NumberOfOwnDescriptors(); i++) {
@@ skipping 223 matching lines @@
       SerializeString_<false, uint8_t>(object);
     } else {
       SerializeString_<false, uc16>(object);
     }
   }
 }
 
 } }  // namespace v8::internal
 
 #endif  // V8_JSON_STRINGIFIER_H_