libvpx: Pull from upstream

source/libvpx/vp9/encoder/vp9_bitstream.h

Index: source/libvpx/vp9/encoder/vp9_bitstream.h
===================================================================
--- source/libvpx/vp9/encoder/vp9_bitstream.h	(revision 290053)
+++ source/libvpx/vp9/encoder/vp9_bitstream.h	(working copy)
@@ -16,12 +16,22 @@
 extern "C" {
 #endif
 
-struct VP9_COMP;
+#include "vp9/encoder/vp9_encoder.h"
 
 void vp9_entropy_mode_init();
 
-void vp9_pack_bitstream(struct VP9_COMP *cpi, uint8_t *dest, size_t *size);
+void vp9_pack_bitstream(VP9_COMP *cpi, uint8_t *dest, size_t *size);
 
+static INLINE int vp9_preserve_existing_gf(VP9_COMP *cpi) {
+  return !cpi->multi_arf_allowed && cpi->refresh_golden_frame &&
+         cpi->rc.is_src_frame_alt_ref &&
+         (!cpi->use_svc ||      // Add spatial svc base layer case here
+          (is_spatial_svc(cpi) &&
+           cpi->svc.spatial_layer_id == 0 &&
+           cpi->svc.layer_context[0].gold_ref_idx >=0 &&
+           cpi->oxcf.ss_play_alternate[0]));
+}
+
 #ifdef __cplusplus
 }  // extern "C"
 #endif