Join embeder threads on Windows.

runtime/bin/process.cc

Index: runtime/bin/process.cc
diff --git a/runtime/bin/process.cc b/runtime/bin/process.cc
index 2c90c11cdbebc29c364aaea4675c86cfc5b14c30..2d9d0ed092674b3c148d7e85a5a2ba2e7305bd3f 100644
--- a/runtime/bin/process.cc
+++ b/runtime/bin/process.cc
@@ -3,6 +3,8 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "bin/dartutils.h"
+#include "bin/dbg_connection.h"
+#include "bin/eventhandler.h"
 #include "bin/io_buffer.h"
 #include "bin/platform.h"
 #include "bin/process.h"
@@ -218,6 +220,8 @@ void FUNCTION_NAME(Process_Exit)(Dart_NativeArguments args) {
   DartUtils::GetInt64Value(Dart_GetNativeArgument(args, 0), &status);
   Dart_ExitIsolate();
   Dart_Cleanup();
+  DebuggerConnectionHandler::StopHandler();
+  EventHandler::Stop();
   exit(static_cast<int>(status));
 }