Add gmock into our dependencies.

third_party/boost/boost/type_traits/ice.hpp

Index: third_party/boost/boost/type_traits/ice.hpp
diff --git a/third_party/boost/boost/type_traits/ice.hpp b/third_party/boost/boost/type_traits/ice.hpp
new file mode 100644
index 0000000000000000000000000000000000000000..134bc4bb76423514c20eb5d09d9742893245d5f0
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+++ b/third_party/boost/boost/type_traits/ice.hpp
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+
+//  (C) Copyright John Maddock and Steve Cleary 2000.
+//  Use, modification and distribution are subject to 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/type_traits for most recent version including documentation.
+//
+//  macros and helpers for working with integral-constant-expressions.
+
+#ifndef BOOST_TT_ICE_HPP_INCLUDED
+#define BOOST_TT_ICE_HPP_INCLUDED
+
+#include <boost/type_traits/detail/yes_no_type.hpp>
+#include <boost/type_traits/detail/ice_or.hpp>
+#include <boost/type_traits/detail/ice_and.hpp>
+#include <boost/type_traits/detail/ice_not.hpp>
+#include <boost/type_traits/detail/ice_eq.hpp>
+
+#endif // BOOST_TT_ICE_HPP_INCLUDED