[V8] Make String::CanMakeExternal ignore the length of new strings

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 5953 matching lines @@
   if (result) {
     DCHECK(obj->IsExternalString());
     isolate->heap()->RegisterExternalString(*obj);
   }
   return result;
 }
 
 
 bool v8::String::CanMakeExternal() {
   i::Handle<i::String> obj = Utils::OpenHandle(this);
-  i::Isolate* isolate = obj->GetIsolate();
+  if (obj->IsExternalString()) return false;
 
   // Old space strings should be externalized.
-  if (!isolate->heap()->new_space()->Contains(*obj)) return true;
-  int size = obj->Size();  // Byte size of the original string.
-  if (size <= i::ExternalString::kShortSize) return false;
-  i::StringShape shape(*obj);
-  return !shape.IsExternal();
+  i::Isolate* isolate = obj->GetIsolate();
+  return !isolate->heap()->new_space()->Contains(*obj);
 }
 
 
 Isolate* v8::Object::GetIsolate() {
   i::Isolate* i_isolate = Utils::OpenHandle(this)->GetIsolate();
   return reinterpret_cast<Isolate*>(i_isolate);
 }
 
 
 Local<v8::Object> v8::Object::New(Isolate* isolate) {
@@ skipping 2786 matching lines @@
   Address callback_address =
       reinterpret_cast<Address>(reinterpret_cast<intptr_t>(callback));
   VMState<EXTERNAL> state(isolate);
   ExternalCallbackScope call_scope(isolate, callback_address);
   callback(info);
 }
 
 
 }  // namespace internal
 }  // namespace v8