Fix a unit test failure of sb8x8 on scaling ref

Disable the use of scaled reference frame for motion search in
SPLITMV mode. This fixes the unit test failure issue triggered
when merging sb8x8 from experimental list.

Change-Id: I02ac25fd8db8d5762f8fee29513b947189875fa0

vp9/encoder/vp9_rdopt.c

diff --git a/vp9/encoder/vp9_rdopt.c b/vp9/encoder/vp9_rdopt.c
index f2cee7f..439905f 100644
--- a/vp9/encoder/vp9_rdopt.c
+++ b/vp9/encoder/vp9_rdopt.c
@@ -4756,6 +4756,21 @@
 
     mbmi->ref_frame = ref_frame;
     mbmi->second_ref_frame = vp9_mode_order[mode_index].second_ref_frame;
+
+    // TODO(jingning): scaling not supported in SPLITMV mode.
+    if (mbmi->ref_frame > 0 &&
+          (yv12_mb[mbmi->ref_frame].y_width != cm->mb_cols * 16 ||
+           yv12_mb[mbmi->ref_frame].y_height != cm->mb_rows * 16) &&
+        this_mode == SPLITMV)
+      continue;
+
+    if (mbmi->second_ref_frame > 0 &&
+          (yv12_mb[mbmi->second_ref_frame].y_width != cm->mb_cols * 16 ||
+           yv12_mb[mbmi->second_ref_frame].y_height != cm->mb_rows * 16) &&
+        this_mode == SPLITMV)
+      continue;
+
+
     set_scale_factors(xd, mbmi->ref_frame, mbmi->second_ref_frame,
                       scale_factor);
     comp_pred = mbmi->second_ref_frame > INTRA_FRAME;