PATENT_GRANT

Google hereby grants to you a perpetual, worldwide, non-exclusive,
no-charge, royalty-free, irrevocable (except as stated in this
section) patent license to make, have made, use, offer to sell, sell,
import, transfer, and otherwise run, modify and propagate the contents
of this implementation, where such license applies only to those
patent claims, both currently owned by Google and acquired in the
future, licensable by Google that are necessarily infringed by this
implementation. This grant does not include claims that would be
infringed only as a consequence of further modification of this
implementation. If you or your agent or exclusive licensee institute
or order or agree to the institution of patent litigation or any other
patent enforcement activity against any entity (including a
cross-claim or counterclaim in a lawsuit) alleging that this
implementation constitutes direct or contributory patent infringement,
or inducement of patent infringement, then any patent rights granted
to you under this License for this implementation shall terminate as
of the date such litigation is filed.