port to use centralized constants files, and add input validation

system_utils.h

Index: system_utils.h
diff --git a/system_utils.h b/system_utils.h
new file mode 100644
index 0000000000000000000000000000000000000000..d07dc198d54680e3387956212a0761f36ececd0e
--- /dev/null
+++ b/system_utils.h
@@ -0,0 +1,32 @@
+// Copyright (c) 2010 The Chromium OS Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef LOGIN_MANAGER_SYSTEM_UTILS_H_
+#define LOGIN_MANAGER_SYSTEM_UTILS_H_
+
+#include <errno.h>
+#include <unistd.h>
+
+#include <base/basictypes.h>
+
+namespace login_manager {
+class SystemUtils {
+ public:
+  SystemUtils() {}
+  virtual ~SystemUtils() {}
+
+  virtual int kill(pid_t pid, int signal) {
+    return ::kill(pid, signal);
+  }
+
+  virtual bool child_is_gone(pid_t child_spec) {
+    return ::waitpid(child_spec, NULL, WNOHANG) == -1 && errno == ECHILD;
+  }
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(SystemUtils);
+};
+}  // namespace login_manager
+
+#endif  // LOGIN_MANAGER_SYSTEM_UTILS_H_