Add gmock into our dependencies.

third_party/boost/boost/type_traits/promote.hpp

Index: third_party/boost/boost/type_traits/promote.hpp
diff --git a/third_party/boost/boost/type_traits/promote.hpp b/third_party/boost/boost/type_traits/promote.hpp
new file mode 100644
index 0000000000000000000000000000000000000000..14efad47eefd0b3d61560b3d0ed8391ea63ca1e5
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+++ b/third_party/boost/boost/type_traits/promote.hpp
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+// Copyright 2005 Alexander Nasonov.
+// 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)
+
+#ifndef FILE_boost_type_traits_promote_hpp_INCLUDED
+#define FILE_boost_type_traits_promote_hpp_INCLUDED
+
+#include <boost/config.hpp>
+#include <boost/type_traits/integral_promotion.hpp>
+#include <boost/type_traits/floating_point_promotion.hpp>
+
+// Should be the last #include
+#include <boost/type_traits/detail/type_trait_def.hpp>
+
+namespace boost {
+
+namespace detail {
+
+template<class T>
+struct promote_impl
+  : integral_promotion<
+        BOOST_DEDUCED_TYPENAME floating_point_promotion<T>::type
+      >
+{
+};
+
+}
+
+BOOST_TT_AUX_TYPE_TRAIT_DEF1(
+      promote
+    , T
+    , BOOST_DEDUCED_TYPENAME boost::detail::promote_impl<T>::type
+    )
+}
+
+#include <boost/type_traits/detail/type_trait_undef.hpp>
+
+#endif // #ifndef FILE_boost_type_traits_promote_hpp_INCLUDED
+