Added read-only file error test.

base/test/test_file_util_posix.cc

Index: base/test/test_file_util_posix.cc
diff --git a/base/test/test_file_util_posix.cc b/base/test/test_file_util_posix.cc
index 0096c9e815df5e3c723012cd5e73b555e176c063..57b4411dcbf0f7e95a5c920210809061d2a0e950 100644
--- a/base/test/test_file_util_posix.cc
+++ b/base/test/test_file_util_posix.cc
@@ -140,4 +140,33 @@ bool MakeFileUnwritable(const FilePath& path) {
   return DenyFilePermission(path, S_IWUSR | S_IWGRP | S_IWOTH);
 }
 
+void* GetPermissionInfo(const FilePath& path, size_t* length) {
+  DCHECK(length != NULL);
+  *length = 0;
+
+  struct stat stat_buf;
+  if (stat(path.value().c_str(), &stat_buf) != 0)
+    return NULL;
+
+  *length = sizeof(mode_t);
+  mode_t* mode = new mode_t;
+  *mode = stat_buf.st_mode;
+
+  return mode;
+}
+
+bool RestorePermissionInfo(const FilePath& path, void* info, size_t length) {
+  if (!info || !length)
+    return false;
+
+  DCHECK_EQ(sizeof(mode_t), length);
+  mode_t* mode = reinterpret_cast<mode_t*>(info);
+
+  int rv = HANDLE_EINTR(chmod(path.value().c_str(), *mode));
+
+  delete mode;  // AKA info.
+
+  return rv == 0;
+}
+
 }  // namespace file_util