Add gmock into our dependencies.

third_party/boost/boost/mpl/sequence_tag_fwd.hpp

Index: third_party/boost/boost/mpl/sequence_tag_fwd.hpp
diff --git a/third_party/boost/boost/mpl/sequence_tag_fwd.hpp b/third_party/boost/boost/mpl/sequence_tag_fwd.hpp
new file mode 100644
index 0000000000000000000000000000000000000000..c6a7c397851f8bd6eb817e912853c090c262ec51
--- /dev/null
+++ b/third_party/boost/boost/mpl/sequence_tag_fwd.hpp
@@ -0,0 +1,26 @@
+
+#ifndef BOOST_MPL_SEQUENCE_TAG_FWD_HPP_INCLUDED
+#define BOOST_MPL_SEQUENCE_TAG_FWD_HPP_INCLUDED
+
+// Copyright Aleksey Gurtovoy 2000-2004
+//
+// 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/libs/mpl for documentation.
+
+// $Source$
+// $Date: 2004-09-02 11:41:37 -0400 (Thu, 02 Sep 2004) $
+// $Revision: 24874 $
+
+namespace boost { namespace mpl {
+
+struct nested_begin_end_tag;
+struct non_sequence_tag;
+
+template< typename Sequence > struct sequence_tag;
+
+}}
+
+#endif // BOOST_MPL_SEQUENCE_TAG_FWD_HPP_INCLUDED