Deserialize the scope chain for background parsing jobs on the main thread

src/background-parsing-task.cc

Index: src/background-parsing-task.cc
diff --git a/src/background-parsing-task.cc b/src/background-parsing-task.cc
index 33d3d518aff0b1fe2b91503e8309f53bd143d772..5df46c82b9049c372b33673b013395274627795d 100644
--- a/src/background-parsing-task.cc
+++ b/src/background-parsing-task.cc
@@ -42,6 +42,9 @@ BackgroundParsingTask::BackgroundParsingTask(
   // Parser needs to stay alive for finalizing the parsing on the main
   // thread.
   source_->parser.reset(new Parser(source_->info.get()));
+  source_->parser->DeserializeScopeChain(
+      source_->info.get(), Handle<Context>::null(),
+      Scope::DeserializationMode::kDeserializeOffHeap);
 }
 
 
@@ -61,9 +64,6 @@ void BackgroundParsingTask::Run() {
   Isolate* isolate = source_->info->isolate();
   source_->info->set_isolate(nullptr);
 
-  source_->parser->DeserializeScopeChain(
-      source_->info.get(), Handle<Context>::null(),
-      Scope::DeserializationMode::kDeserializeOffHeap);
   source_->parser->ParseOnBackground(source_->info.get());
 
   if (script_data_ != nullptr) {