Properly reset x->cb_offset

BUG=aomedia:1227

Change-Id: If44e819b1607e9037de7ee520b7263dc668ab4d8

av1/encoder/encodeframe.c

diff --git a/av1/encoder/encodeframe.c b/av1/encoder/encodeframe.c
index e7f280d..f8cf9b4 100644
--- a/av1/encoder/encodeframe.c
+++ b/av1/encoder/encodeframe.c
@@ -1883,6 +1883,7 @@
       // int rate_coeffs = 0;
       // encode_sb(cpi, td, tile_data, tp, mi_row, mi_col, DRY_RUN_COSTCOEFFS,
       //           bsize, pc_tree, &rate_coeffs);
+      x->cb_offset = 0;
       encode_sb(cpi, td, tile_data, tp, mi_row, mi_col, OUTPUT_ENABLED, bsize,
                 pc_tree, NULL);
     } else {
@@ -3365,7 +3366,6 @@
       pc_tree->index != 3) {
     if (bsize == cm->seq_params.sb_size) {
       x->cb_offset = 0;
-
       encode_sb(cpi, td, tile_data, tp, mi_row, mi_col, OUTPUT_ENABLED, bsize,
                 pc_tree, NULL);
     } else {