Introduce a PrototypeIterator template and use it all over the place

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"
+#include "src/prototype-iterator.h"
 #include "src/utils.h"
 
 namespace v8 {
 namespace internal {
 
 class BasicJsonStringifier BASE_EMBEDDED {
  public:
   explicit BasicJsonStringifier(Isolate* isolate);
 
   MUST_USE_RESULT MaybeHandle<Object> Stringify(Handle<Object> object);
@@ skipping 602 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_);
+    object = Handle<JSObject>(JSObject::cast(SAFE_GET_PROTOTYPE_FAST(*object)),
+                              isolate_);
     ASSERT(object->IsGlobalObject());
   }
 
   Append('{');
   bool comma = false;
 
   if (object->HasFastProperties() &&
       !object->HasIndexedInterceptor() &&
       !object->HasNamedInterceptor() &&
       object->elements()->length() == 0) {
@@ skipping 225 matching lines @@
       SerializeString_<false, uint8_t>(object);
     } else {
       SerializeString_<false, uc16>(object);
     }
   }
 }
 
 } }  // namespace v8::internal
 
 #endif  // V8_JSON_STRINGIFIER_H_