Fix deadlock in process exit handling

runtime/bin/process.cc

Index: runtime/bin/process.cc
diff --git a/runtime/bin/process.cc b/runtime/bin/process.cc
index 6ae139972ca6471911ca978fc48f442289782da0..484316bdf2061548b57d7514bc187086258ea7c8 100644
--- a/runtime/bin/process.cc
+++ b/runtime/bin/process.cc
@@ -61,6 +61,7 @@ void FUNCTION_NAME(Process_Start)(Dart_NativeArguments args) {
   Dart_ExitScope();
 }
 
+
 void FUNCTION_NAME(Process_Kill)(Dart_NativeArguments args) {
   Dart_EnterScope();
   intptr_t pid = DartUtils::GetIntegerValue(Dart_GetNativeArgument(args, 1));
@@ -68,3 +69,11 @@ void FUNCTION_NAME(Process_Kill)(Dart_NativeArguments args) {
   Dart_SetReturnValue(args, Dart_NewBoolean(success));
   Dart_ExitScope();
 }
+
+
+void FUNCTION_NAME(Process_Exit)(Dart_NativeArguments args) {
+  Dart_EnterScope();
+  intptr_t pid = DartUtils::GetIntegerValue(Dart_GetNativeArgument(args, 1));
+  Process::Exit(pid);
+  Dart_ExitScope();
+}