libvpx: Pull from upstream

source/libvpx/third_party/libwebm/PATENTS.TXT

Index: source/libvpx/third_party/libwebm/PATENTS.TXT
===================================================================
--- source/libvpx/third_party/libwebm/PATENTS.TXT	(revision 0)
+++ source/libvpx/third_party/libwebm/PATENTS.TXT	(revision 0)
@@ -0,0 +1,22 @@
+Additional IP Rights Grant (Patents)
+
+"This implementation" means the copyrightable works distributed by
+Google as part of the WebM Project.
+
+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 of VP8, 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 of VP8. 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 against any
+entity (including a cross-claim or counterclaim in a lawsuit) alleging
+that this implementation of VP8 or any code incorporated within this
+implementation of VP8 constitutes direct or contributory patent
+infringement, or inducement of patent infringement, then any patent
+rights granted to you under this License for this implementation of VP8
+shall terminate as of the date such litigation is filed.