[modules] Allow resolve-callback to signal failure.

include/v8.h

Index: include/v8.h
diff --git a/include/v8.h b/include/v8.h
index accc280c32c0c715cf7bc2db4616c763d40e52ae..2a747957958a4cb08eee92ed7634b518fc3aaad7 100644
--- a/include/v8.h
+++ b/include/v8.h
@@ -1095,7 +1095,8 @@ class V8_EXPORT Module {
   /**
    * ModuleDeclarationInstantiation
    *
-   * Returns false if an exception occurred during instantiation.
+   * Returns false if an exception occurred during instantiation. (In the case
+   * where the callback throws an exception, that exception is propagated.)
    */
   V8_WARN_UNUSED_RESULT bool Instantiate(Local<Context> context,
                                          ResolveCallback callback);