Add gmock into our dependencies.

third_party/boost/boost/preprocessor/control/expr_iif.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_CONTROL_EXPR_IIF_HPP
+# define BOOST_PREPROCESSOR_CONTROL_EXPR_IIF_HPP
+#
+# include <boost/preprocessor/config/config.hpp>
+#
+# /* BOOST_PP_EXPR_IIF */
+#
+# if ~BOOST_PP_CONFIG_FLAGS() & BOOST_PP_CONFIG_MWCC()
+#    define BOOST_PP_EXPR_IIF(bit, expr) BOOST_PP_EXPR_IIF_I(bit, expr)
+# else
+#    define BOOST_PP_EXPR_IIF(bit, expr) BOOST_PP_EXPR_IIF_OO((bit, expr))
+#    define BOOST_PP_EXPR_IIF_OO(par) BOOST_PP_EXPR_IIF_I ## par
+# endif
+#
+# define BOOST_PP_EXPR_IIF_I(bit, expr) BOOST_PP_EXPR_IIF_ ## bit(expr)
+#
+# define BOOST_PP_EXPR_IIF_0(expr)
+# define BOOST_PP_EXPR_IIF_1(expr) expr
+#
+# endif