[ESNext] Implement DynamicImportCall

src/isolate.cc

Index: src/isolate.cc
diff --git a/src/isolate.cc b/src/isolate.cc
index bb59b5e7dce4a0c45d9b2606565d9f1631852675..b62fb8d0df4fb7b8b1b0277a039e7c483487413e 100644
--- a/src/isolate.cc
+++ b/src/isolate.cc
@@ -3341,6 +3341,21 @@ void Isolate::DebugStateUpdated() {
   promise_hook_or_debug_is_active_ = promise_hook_ || debug()->is_active();
 }
 
+void Isolate::RunHostImportModuleDynamicallyCallback(
+    Handle<String> source_url, Handle<String> specifier,
+    Handle<JSPromise> promise) {
+  if (host_import_module_dynamically_callback_ == nullptr) return;

[neis, 2017/03/17 10:36:32]

I think we talked about this case. Didn't we agree to fail here?

[gsathya, 2017/03/17 21:47:59]

I'm not sure tbh. there could be cases where the embedder doesnt want to
implement this? Also not sure how to sync this change with blink if we fail. I
was going to ask Jochen about this.

[neis, 2017/03/20 09:36:03]

Hmm, I would imagine that if an embedder for some reason doesn't want to support
dynamic imports, they just do that by making the callback always do
FinishDynamicImportFailure. But I would be interested to hear what Jochen and
Adam think.

[gsathya, 2017/03/22 03:08:34]

Jochen --

For dynamic import to work, we require that the embedder register a callback to
load files. 

1) Should the API be something like
isolate->SetHostImportModuleDynamicallyCallback(callback) or have the callback
set up as part of creating the isolate using create_params (which is what I've
implemented here).

2) What if the embedder doesn't implement the API? Should we crash when import
is used (for the former approach using SetHostImportModuleDyanamicallyCallback)
or on isolate creation (for the create_params approach)?

This is part of the syntax defined by the language so should we even allow the
creation of an isolate without this callback?

+
+  host_import_module_dynamically_callback_(
+      reinterpret_cast<v8::Isolate*>(this), v8::Utils::ToLocal(source_url),
+      v8::Utils::ToLocal(specifier), v8::Utils::PromiseToLocal(promise));
+}
+
+void Isolate::SetHostImportModuleDynamicallyCallback(
+    HostImportModuleDynamicallyCallback callback) {
+  host_import_module_dynamically_callback_ = callback;
+}
+
 void Isolate::SetPromiseHook(PromiseHook hook) {
   promise_hook_ = hook;
   DebugStateUpdated();