libvpx: Pull from upstream

source/libvpx/webmdec.cc

Index: source/libvpx/webmdec.cc
diff --git a/source/libvpx/webmdec.cc b/source/libvpx/webmdec.cc
index 4383e8efd8d995e4ba327493935fd6f1ee2dc6dd..d591f3e3d7413f9b12b9f609eb31c79e958a95f8 100644
--- a/source/libvpx/webmdec.cc
+++ b/source/libvpx/webmdec.cc
@@ -41,6 +41,7 @@ void reset(struct WebmInputContext *const webm_ctx) {
   webm_ctx->block_frame_index = 0;
   webm_ctx->video_track_index = 0;
   webm_ctx->timestamp_ns = 0;
+  webm_ctx->is_key_frame = false;
 }
 
 void get_first_cluster(struct WebmInputContext *const webm_ctx) {
@@ -182,6 +183,7 @@ int webm_read_frame(struct WebmInputContext *webm_ctx,
   }
   *bytes_in_buffer = frame.len;
   webm_ctx->timestamp_ns = block->GetTime(cluster);
+  webm_ctx->is_key_frame = block->IsKey();
 
   mkvparser::MkvReader *const reader =
       reinterpret_cast<mkvparser::MkvReader*>(webm_ctx->reader);