Dart: Removes C++ set for closing handles on an unhandled exception.

mojo/dart/embedder/dart_controller.cc

Index: mojo/dart/embedder/dart_controller.cc
diff --git a/mojo/dart/embedder/dart_controller.cc b/mojo/dart/embedder/dart_controller.cc
index 16f4858dd8e16afb7f233c866856f20186382d07..14868c9aa8e78f55faa70eb51f38c73e718cc260 100644
--- a/mojo/dart/embedder/dart_controller.cc
+++ b/mojo/dart/embedder/dart_controller.cc
@@ -258,8 +258,12 @@ static void RunIsolate(Dart_Isolate isolate,
   DART_CHECK_VALID(result);
 
   result = Dart_RunLoop();
+
+  // Here we log the error, but we don't do DART_CHECK_VALID because we don't
+  // want to bring the whole process down due to an error in application code,
+  // whereas above we do want to bring the whole process down for a bug in
+  // library or generated code.
   tonic::LogIfError(result);
-  DART_CHECK_VALID(result);
 }
 
 Dart_Handle DartController::LibraryTagHandler(Dart_LibraryTag tag,
@@ -444,19 +448,26 @@ void DartController::IsolateShutdownCallback(void* callback_data) {
 }
 
 void DartController::UnhandledExceptionCallback(Dart_Handle error) {
+  Dart_Handle mojo_core_lib =
+      Builtin::GetLibrary(Builtin::kMojoInternalLibrary);
+  DART_CHECK_VALID(mojo_core_lib);
+  Dart_Handle handle_natives_type =
+      Dart_GetType(mojo_core_lib,
+                   Dart_NewStringFromCString("MojoHandleNatives"), 0, nullptr);
+  DART_CHECK_VALID(handle_natives_type);
+  Dart_Handle method_name = Dart_NewStringFromCString("_closeUnclosedHandles");
+  CHECK(!Dart_IsError(method_name));
+  Dart_Handle result =
+      Dart_Invoke(handle_natives_type, method_name, 0, nullptr);
+  DART_CHECK_VALID(result);
+
   auto isolate_data = MojoDartState::Current();
   if (!isolate_data->callbacks().exception.is_null()) {
-    // TODO(zra): Instead of passing an error handle, it may make life easier
-    // for clients if we pass any error string here instead.
-    isolate_data->callbacks().exception.Run(error);
-  }
-
-  // Close handles generated by the isolate.
-  std::set<MojoHandle>& handles = isolate_data->unclosed_handles();
-  for (auto it = handles.begin(); it != handles.end(); ++it) {
-    MojoClose((*it));
+    int64_t handles_closed = 0;
+    Dart_Handle int_result = Dart_IntegerToInt64(result, &handles_closed);
+    DART_CHECK_VALID(int_result);
+    isolate_data->callbacks().exception.Run(error, handles_closed);
   }
-  handles.clear();
 }