Move Maps' back pointers from "transitions" to "constructor" field

src/api.cc

 // 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.
 
 #include "src/api.h"
 
 #include <string.h>  // For memcpy, strlen.
 #ifdef V8_USE_ADDRESS_SANITIZER
 #include <sanitizer/asan_interface.h>
 #endif  // V8_USE_ADDRESS_SANITIZER
@@ skipping 2553 matching lines @@
         value <= i::kMaxUInt32 &&
         value == i::FastUI2D(i::FastD2UI(value));
   }
   return false;
 }
 
 
 static bool CheckConstructor(i::Isolate* isolate,
                              i::Handle<i::JSObject> obj,
                              const char* class_name) {
-  i::Handle<i::Object> constr(obj->map()->constructor(), isolate);
+  i::Handle<i::Object> constr(obj->map()->GetConstructor(), isolate);
   if (!constr->IsJSFunction()) return false;
   i::Handle<i::JSFunction> func = i::Handle<i::JSFunction>::cast(constr);
   return func->shared()->native() && constr.is_identical_to(
       i::Object::GetProperty(isolate,
                              isolate->js_builtins_object(),
                              class_name).ToHandleChecked());
 }
 
 
 bool Value::IsNativeError() const {
@@ skipping 5190 matching lines @@
   Isolate* isolate = reinterpret_cast<Isolate*>(info.GetIsolate());
   Address callback_address =
       reinterpret_cast<Address>(reinterpret_cast<intptr_t>(callback));
   VMState<EXTERNAL> state(isolate);
   ExternalCallbackScope call_scope(isolate, callback_address);
   callback(info);
 }
 
 
 } }  // namespace v8::internal