WIP: Allow ValueSerializer clients to transfer long strings out of band.

src/api.cc

Index: src/api.cc
diff --git a/src/api.cc b/src/api.cc
index c7ec5722e4f6e52c89fe8355cd4f9a130df9737e..2804e95f316adfc32689d51dbee508b4100ce503 100644
--- a/src/api.cc
+++ b/src/api.cc
@@ -3130,6 +3130,15 @@ Maybe<uint32_t> ValueSerializer::Delegate::GetWasmModuleTransferId(
   return Nothing<uint32_t>();
 }
 
+Maybe<uint32_t> ValueSerializer::Delegate::GetLongStringId(
+    Isolate* v8_isolate, Local<String> string) {
+  i::Isolate* isolate = reinterpret_cast<i::Isolate*>(v8_isolate);
+  isolate->ScheduleThrow(*isolate->factory()->NewError(
+      isolate->error_function(), i::MessageTemplate::kDataCloneError,
+      Utils::OpenHandle(*string)));
+  return Nothing<uint32_t>();
+}
+
 void* ValueSerializer::Delegate::ReallocateBufferMemory(void* old_buffer,
                                                         size_t size,
                                                         size_t* actual_size) {
@@ -3163,6 +3172,10 @@ void ValueSerializer::SetTreatArrayBufferViewsAsHostObjects(bool mode) {
   private_->serializer.SetTreatArrayBufferViewsAsHostObjects(mode);
 }
 
+void ValueSerializer::SetMinimumLongStringLength(int length) {
+  private_->serializer.SetMinimumLongStringLength(length);
+}
+
 Maybe<bool> ValueSerializer::WriteValue(Local<Context> context,
                                         Local<Value> value) {
   PREPARE_FOR_EXECUTION_PRIMITIVE(context, ValueSerializer, WriteValue, bool);
@@ -3328,6 +3341,13 @@ void ValueDeserializer::TransferSharedArrayBuffer(
       transfer_id, Utils::OpenHandle(*shared_array_buffer));
 }
 
+void ValueDeserializer::TransferLongString(uint32_t transfer_id,
+                                           Local<String> string) {
+  CHECK(!private_->has_aborted);
+  private_->deserializer.TransferLongString(transfer_id,
+                                            Utils::OpenHandle(*string));
+}
+
 bool ValueDeserializer::ReadUint32(uint32_t* value) {
   return private_->deserializer.ReadUint32(value);
 }