Fix deadlock in process exit handling

runtime/bin/process.cc

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "bin/dartutils.h"
 #include "bin/process.h"
 
 #include "include/dart_api.h"
 
 void FUNCTION_NAME(Process_Start)(Dart_NativeArguments args) {
@@ skipping 43 matching lines @@
     DartUtils::SetIntegerInstanceField(
         status_handle, "_errorCode", error_code);
     DartUtils::SetStringInstanceField(
         status_handle, "_errorMessage", os_error_message);
   }
   delete[] string_args;
   Dart_SetReturnValue(args, Dart_NewBoolean(error_code == 0));
   Dart_ExitScope();
 }
 
+
 void FUNCTION_NAME(Process_Kill)(Dart_NativeArguments args) {
   Dart_EnterScope();
   intptr_t pid = DartUtils::GetIntegerValue(Dart_GetNativeArgument(args, 1));
   bool success = Process::Kill(pid);
   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();
+}