Make exception thrown via v8 public API propagate to v8::TryCatch as JS thrown exceptions do.

src/messages.cc

Index: src/messages.cc
diff --git a/src/messages.cc b/src/messages.cc
index 42fc3c9bd66fdd2742983340db3b41b0ad158114..8034798cb09aedc4d16b29b4d3508292ef91c39b 100644
--- a/src/messages.cc
+++ b/src/messages.cc
@@ -128,12 +128,23 @@ Handle<Object> MessageHandler::MakeMessageObject(
 
 void MessageHandler::ReportMessage(MessageLocation* loc,
                                    Handle<Object> message) {
+  // We are calling into embedder's code which can throw exceptions.
+  // Thus we need to save current exception state, reset it to the clean one
+  // and ignore scheduled exceptions callbacks can throw.
+  Top::ExceptionScope exception_scope;
+  Top::clear_pending_exception();
+  Top::set_external_caught_exception(false);
+
   v8::Local<v8::Message> api_message_obj = v8::Utils::MessageToLocal(message);
 
   v8::NeanderArray global_listeners(Factory::message_listeners());
   int global_length = global_listeners.length();
   if (global_length == 0) {
     DefaultMessageReport(loc, message);
+    if (Top::has_scheduled_exception()) {
+      // Consider logging it somehow.
+      Top::clear_scheduled_exception();
+    }
   } else {
     for (int i = 0; i < global_length; i++) {
       HandleScope scope;
@@ -144,6 +155,10 @@ void MessageHandler::ReportMessage(MessageLocation* loc,
           FUNCTION_CAST<v8::MessageCallback>(callback_obj->proxy());
       Handle<Object> callback_data(listener.get(1));
       callback(api_message_obj, v8::Utils::ToLocal(callback_data));
+      if (Top::has_scheduled_exception()) {
+        // Consider logging it somehow.
+        Top::clear_scheduled_exception();
+      }
     }
   }
 }