dart2js: throw when receiving an internal-problem error from the FE.

pkg/compiler/lib/src/kernel/front_end_adapter.dart

Index: pkg/compiler/lib/src/kernel/front_end_adapter.dart
diff --git a/pkg/compiler/lib/src/kernel/front_end_adapter.dart b/pkg/compiler/lib/src/kernel/front_end_adapter.dart
index b2bc3ee390243e11ac71946cb9812ec583e25ceb..17fd4f3a41ce4eb16dd26ca27d89ba97d775566a 100644
--- a/pkg/compiler/lib/src/kernel/front_end_adapter.dart
+++ b/pkg/compiler/lib/src/kernel/front_end_adapter.dart
@@ -81,8 +81,9 @@ void reportFrontEndMessage(
   // TODO(sigmund): translate message kinds using message.dart2jsCode
   MessageKind kind = MessageKind.GENERIC;
   switch (message.severity) {
-    case fe.Severity.error:
     case fe.Severity.internalProblem:
+      throw message.message;
+    case fe.Severity.error:
       reporter.reportErrorMessage(
           NO_LOCATION_SPANNABLE, kind, {'text': message.message});
       break;