Validate MessageHeader before using

mojo/public/cpp/test_support/lib/test_support.cc

+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "mojo/public/cpp/test_support/test_support.h"
+
+#include <stdlib.h>
+
+namespace mojo {
+namespace test {
+
+std::vector<std::string> EnumerateSourceRootRelativeDirectory(
+    const std::string& relative_path) {
+  char** names = MojoTestSupportEnumerateSourceRootRelativeDirectory(
+      relative_path.c_str());
+  std::vector<std::string> results;
+  for (char** ptr = names; *ptr != NULL; ++ptr) {
+    results.push_back(*ptr);
+    free(*ptr);
+  }
+  free(names);
+  return results;
+}
+
+}  // namespace test
+}  // namespace mojo