Add gmock into our dependencies.

third_party/boost/boost/preprocessor/slot/slot.hpp

+# /* **************************************************************************
+#  *                                                                          *
+#  *     (C) Copyright Paul Mensonides 2002.
+#  *     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 for most recent version. */
+#
+# ifndef BOOST_PREPROCESSOR_SLOT_SLOT_HPP
+# define BOOST_PREPROCESSOR_SLOT_SLOT_HPP
+#
+# include <boost/preprocessor/cat.hpp>
+# include <boost/preprocessor/slot/detail/def.hpp>
+#
+# /* BOOST_PP_ASSIGN_SLOT */
+#
+# define BOOST_PP_ASSIGN_SLOT(i) BOOST_PP_CAT(BOOST_PP_ASSIGN_SLOT_, i)
+#
+# define BOOST_PP_ASSIGN_SLOT_1 <boost/preprocessor/slot/detail/slot1.hpp>
+# define BOOST_PP_ASSIGN_SLOT_2 <boost/preprocessor/slot/detail/slot2.hpp>
+# define BOOST_PP_ASSIGN_SLOT_3 <boost/preprocessor/slot/detail/slot3.hpp>
+# define BOOST_PP_ASSIGN_SLOT_4 <boost/preprocessor/slot/detail/slot4.hpp>
+# define BOOST_PP_ASSIGN_SLOT_5 <boost/preprocessor/slot/detail/slot5.hpp>
+#
+# /* BOOST_PP_SLOT */
+#
+# define BOOST_PP_SLOT(i) BOOST_PP_CAT(BOOST_PP_SLOT_, i)()
+#
+# endif