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

third_party/WebKit/Source/core/dom/ModuleScript.h

Index: third_party/WebKit/Source/core/dom/ModuleScript.h
diff --git a/third_party/WebKit/Source/core/dom/ModuleScript.h b/third_party/WebKit/Source/core/dom/ModuleScript.h
index f33417973291c05e410a8cb418bb2b368a32035e..9b4efa65d9d4e4ea4ae69fef993d420c6854eb72 100644
--- a/third_party/WebKit/Source/core/dom/ModuleScript.h
+++ b/third_party/WebKit/Source/core/dom/ModuleScript.h
@@ -56,6 +56,10 @@ class CORE_EXPORT ModuleScript final : public Script, public TraceWrapperBase {
   // https://html.spec.whatwg.org/multipage/webappapis.html#internal-module-script-graph-fetching-procedure
   void SetInstantiationSuccess();
 
+  v8::Local<v8::Value> CreateInstantiationError(v8::Isolate* isolate) const {

[hiroshige, 2017/04/27 22:56:40]

ModulatorImpl::GetInstantiationError() and
ModuleScript::CreateInstantiationError() looks quite similar in its
interface and developers might be not sure which function to use.

I expect GetInstantiationError() should be preferred because it enforces
the correct |isolate| to be used, if we use the correct modulator.
So how about renaming CreateInstantiationError() to something like
CreateInstantiationErrorInternal() and adding a comment that this should
be used only from ModulatorImpl::GetInstantiationError()?

[kouhei (in TOK), 2017/04/28 00:55:09]

Yes. That's the idea. Done.

[hiroshige, 2017/04/28 01:28:35]

nit: Probably unifying the Create...() and Get...() prefixes might be better.

+    return instantiation_error_.NewLocal(isolate);
+  }
+
   ParserDisposition ParserState() const { return parser_state_; }
   WebURLRequest::FetchCredentialsMode CredentialsMode() const {
     return credentials_mode_;