Bug 1820119 - import() should throw a TypeError in a worklet script. r=jonco,yulia

Differential Revision: https://phabricator.services.mozilla.com/D171563

js/loader/ModuleLoaderBase.cpp

@@ -318,7 +318,10 @@ bool ModuleLoaderBase::HostImportModuleDynamically(
       aCx, uri, script, aReferencingPrivate, specifierString, aPromise);
 
   if (!request) {
-    JS_ReportErrorASCII(aCx, "Dynamic import not supported in this context");
+    // Throws TypeError if CreateDynamicImport returns nullptr.
+    JS_ReportErrorNumberASCII(aCx, js::GetErrorMessage, nullptr,
+                              JSMSG_DYNAMIC_IMPORT_NOT_SUPPORTED);
+
     return false;
   }