1. Get rid of SwitchIsolateScope as it is not clear when this should be used and there is also a bu…

runtime/vm/dart_api_impl.cc

Index: runtime/vm/dart_api_impl.cc
diff --git a/runtime/vm/dart_api_impl.cc b/runtime/vm/dart_api_impl.cc
index f25747cdd707c74414acb52d4c3e7951e379e94c..bd24209a73f60daf4f9d09483ed6512e37d5c98c 100644
--- a/runtime/vm/dart_api_impl.cc
+++ b/runtime/vm/dart_api_impl.cc
@@ -1664,8 +1664,9 @@ DART_EXPORT Dart_Handle Dart_RunLoop() {
   Monitor monitor;
   MonitorLocker ml(&monitor);
   {
-    SwitchIsolateScope switch_scope(NULL);
-
+    // The message handler run loop does not expect to have a current isolate
+    // so we exit the isolate here and enter it again after the runloop is done.
+    Thread::ExitIsolate();
     RunLoopData data;
     data.monitor = &monitor;
     data.done = false;
@@ -1675,6 +1676,7 @@ DART_EXPORT Dart_Handle Dart_RunLoop() {
     while (!data.done) {
       ml.Wait();
     }
+    Thread::EnterIsolate(I);
   }
   if (I->object_store()->sticky_error() != Object::null()) {
     Dart_Handle error = Api::NewHandle(I, I->object_store()->sticky_error());