[intra-edge] Convert 4x4 VP9 to ext-intra; upsample edge samples

Updates to intra-edge experiment

- Convert VP9-style intra pred to Ext-intra style
- Upsample edge predictors by 2x based on angle and edge size

BD-rate, 1-kf AWCY
  360p:  -0.11%
  720p:  -0.54
  1080p: -0.96

Change-Id: Ib73805d31d5d286e607a7ee7470fcbdf11edbbff
diff --git a/av1/encoder/bitstream.c b/av1/encoder/bitstream.c
index 0385221..016722a 100644
--- a/av1/encoder/bitstream.c
+++ b/av1/encoder/bitstream.c
@@ -1451,7 +1451,7 @@
 #endif  // CONFIG_INTRA_INTERP
 
   (void)ec_ctx;
-  if (bsize < BLOCK_8X8) return;
+  if (!av1_use_angle_delta(bsize)) return;
 
   if (av1_is_directional_mode(mbmi->mode, bsize)) {
     write_uniform(w, 2 * MAX_ANGLE_DELTA + 1,