Add gmock into our dependencies.

third_party/boost/boost/mpl/tag.hpp

Index: third_party/boost/boost/mpl/tag.hpp
diff --git a/third_party/boost/boost/mpl/tag.hpp b/third_party/boost/boost/mpl/tag.hpp
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index 0000000000000000000000000000000000000000..e061703fd9c6f449888b614eca68909a552e276a
--- /dev/null
+++ b/third_party/boost/boost/mpl/tag.hpp
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+
+#ifndef BOOST_MPL_TAG_HPP_INCLUDED
+#define BOOST_MPL_TAG_HPP_INCLUDED
+
+// Copyright Aleksey Gurtovoy 2004
+//
+// Distributed under the Boost Software License, Version 1.0. 
+// (See accompanying file LICENSE_1_0.txt or copy at 
+// http://www.boost.org/LICENSE_1_0.txt)
+//
+// See http://www.boost.org/libs/mpl for documentation.
+
+// $Source$
+// $Date: 2004-09-02 11:41:37 -0400 (Thu, 02 Sep 2004) $
+// $Revision: 24874 $
+
+#include <boost/mpl/eval_if.hpp>
+#include <boost/mpl/void.hpp>
+#include <boost/mpl/aux_/has_tag.hpp>
+#include <boost/mpl/aux_/config/eti.hpp>
+
+namespace boost { namespace mpl {
+
+namespace aux {
+template< typename T > struct tag_impl
+{
+    typedef typename T::tag type;
+};
+}
+
+template< typename T, typename Default = void_ > struct tag
+#if !defined(BOOST_MPL_CFG_MSVC_ETI_BUG)
+    : if_< 
+          aux::has_tag<T>
+        , aux::tag_impl<T>
+        , Default
+        >::type
+{
+#else
+{
+    typedef typename eval_if< 
+          aux::has_tag<T>
+        , aux::tag_impl<T>
+        , Default
+        >::type type;
+
+#endif
+};
+
+}}
+
+#endif // BOOST_MPL_TAG_HPP_INCLUDED