Compute strongest Sobel x and y edge component

Change-Id: I731975a3f5e49602a5e370e9aa6fa5b8dc01ce6a
diff --git a/av1/encoder/block.h b/av1/encoder/block.h
index 87761e9..e96ca16 100644
--- a/av1/encoder/block.h
+++ b/av1/encoder/block.h
@@ -416,6 +416,9 @@
   // detection). For reference, 556 is the value returned for a solid
   // vertical black/white edge.
   uint16_t edge_strength;
+  // The strongest edge strength seen along the x/y axis.
+  uint16_t edge_strength_x;
+  uint16_t edge_strength_y;
 
   // [Saved stat index]
   COMP_RD_STATS comp_rd_stats[MAX_COMP_RD_STATS];