Add gmock into our dependencies.

third_party/boost/boost/fusion/support/detail/category_of.hpp

Index: third_party/boost/boost/fusion/support/detail/category_of.hpp
diff --git a/third_party/boost/boost/fusion/support/detail/category_of.hpp b/third_party/boost/boost/fusion/support/detail/category_of.hpp
new file mode 100644
index 0000000000000000000000000000000000000000..04102cfdf1c70ae8e60f2651f19a0723cbb32915
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+++ b/third_party/boost/boost/fusion/support/detail/category_of.hpp
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+/*=============================================================================
+    Copyright (c) 2001-2006 Joel de Guzman
+
+    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)
+==============================================================================*/
+#if !defined(FUSION_CATEGORY_OF_07212005_1025)
+#define FUSION_CATEGORY_OF_07212005_1025
+
+namespace boost { namespace fusion { namespace detail
+{
+    template <typename T>
+    struct fusion_category_of
+    {
+        typedef typename T::category type;
+    };
+}}}
+
+#endif