Make it possible to run gtests on iOS.

base/test/main_hook.cc

Index: base/test/main_hook.cc
diff --git a/base/test/main_hook.cc b/base/test/main_hook.cc
new file mode 100644
index 0000000000000000000000000000000000000000..f1f196160d52da36db7a34ac3e9c8c8e7d17a19c
--- /dev/null
+++ b/base/test/main_hook.cc
@@ -0,0 +1,9 @@
+// Copyright (c) 2012 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 "base/test/main_hook.h"
+
+#if !defined(OS_IOS)
+MainHook::MainHook(MainType main_func, int argc, char* argv[]) {}
+#endif