[ES6 modules] Return previous error when an instantiation is reattempt.

third_party/WebKit/Source/core/dom/ModulatorImpl.cpp

 // Copyright 2017 The Chromium 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 "core/dom/ModulatorImpl.h"
 
 #include "core/dom/Document.h"
 #include "core/dom/ExecutionContext.h"
 #include "core/dom/ModuleMap.h"
 #include "core/dom/ModuleScript.h"
@@ skipping 110 matching lines @@
   ScriptState::Scope scope(script_state_.Get());
   return ScriptModule::Compile(script_state_->GetIsolate(), script_source,
                                url_str, access_control_status);
 }
 
 ScriptValue ModulatorImpl::InstantiateModule(ScriptModule script_module) {
   ScriptState::Scope scope(script_state_.Get());
   return script_module.Instantiate(script_state_.Get());
 }
 
+ScriptValue ModulatorImpl::GetInstantiationError(
+    const ModuleScript* module_script) {
+  ScriptState::Scope scope(script_state_.Get());
+  return ScriptValue(
+      script_state_.Get(),
+      module_script->CreateInstantiationError(script_state_->GetIsolate()));
+}
+
 Vector<String> ModulatorImpl::ModuleRequestsFromScriptModule(
     ScriptModule script_module) {
   ScriptState::Scope scope(script_state_.Get());
   return script_module.ModuleRequests(script_state_.Get());
 }
 
 inline ExecutionContext* ModulatorImpl::GetExecutionContext() const {
   return ExecutionContext::From(script_state_.Get());
 }
 
 DEFINE_TRACE(ModulatorImpl) {
   Modulator::Trace(visitor);
   visitor->Trace(fetcher_);
   visitor->Trace(map_);
   visitor->Trace(loader_registry_);
   visitor->Trace(tree_linker_registry_);
   visitor->Trace(script_module_resolver_);
 }
 
 DEFINE_TRACE_WRAPPERS(ModulatorImpl) {
   visitor->TraceWrappers(map_);
 }
 
 }  // namespace blink