Add a WriteStringToFile overload that cares about permissions.

Change-Id: I857a80b61768d4e9610bdd149eff2d9d8e48d2c0
diff --git a/include/utils/file.h b/include/utils/file.h
index 108cabc..d6b7057 100644
--- a/include/utils/file.h
+++ b/include/utils/file.h
@@ -18,11 +18,14 @@
 #define UTILS_FILE_H
 
 #include <string>
+#include <sys/stat.h>
 
 namespace android {
 
 bool ReadFileToString(const std::string& path, std::string* content);
 bool WriteStringToFile(const std::string& content, const std::string& path);
+bool WriteStringToFile(const std::string& content, const std::string& path,
+                       mode_t mode, uid_t owner, gid_t group);
 
 } // namespace android