rtc: Avoid scene detection on resize

Don't enter scene detection under external resize.
Add rc->prev_coded_width/height to track the
previous encoded frame eweight/height.
The rc is part of layer context so this will be
per spatial layer for SVC.

This fixes the buffer overflow issue below.

Bug: chromium:1393384
Change-Id: I4b11818a27c439c2d2c42036dff7b8777f70a86e
(cherry picked from commit bee1caded272127a6d6b70ac79479083d183d5d0)

av1/encoder/ratectrl.c

diff --git a/av1/encoder/ratectrl.c b/av1/encoder/ratectrl.c
index e6bb184..d3ce895 100644
--- a/av1/encoder/ratectrl.c
+++ b/av1/encoder/ratectrl.c
@@ -2160,6 +2160,9 @@
   }
 #endif
   if (current_frame->frame_type == KEY_FRAME) rc->frames_since_key = 0;
+
+  rc->prev_coded_width = cm->width;
+  rc->prev_coded_height = cm->height;
   // if (current_frame->frame_number == 1 && cm->show_frame)
   /*
   rc->this_frame_target =
@@ -2176,6 +2179,8 @@
   cpi->rc.rc_2_frame = 0;
   cpi->rc.rc_1_frame = 0;
   cpi->rc.prev_avg_frame_bandwidth = cpi->rc.avg_frame_bandwidth;
+  cpi->rc.prev_coded_width = cpi->common.width;
+  cpi->rc.prev_coded_height = cpi->common.height;
 }
 
 int av1_find_qindex(double desired_q, aom_bit_depth_t bit_depth,
@@ -3120,8 +3125,15 @@
     }
   }
   // Check for scene change: for SVC check on base spatial layer only.
-  if (cpi->sf.rt_sf.check_scene_detection && svc->spatial_layer_id == 0)
-    rc_scene_detection_onepass_rt(cpi, frame_input);
+  if (cpi->sf.rt_sf.check_scene_detection && svc->spatial_layer_id == 0) {
+    if (rc->prev_coded_width == cm->width &&
+        rc->prev_coded_height == cm->height) {
+      rc_scene_detection_onepass_rt(cpi, frame_input);
+    } else if (cpi->src_sad_blk_64x64) {
+      aom_free(cpi->src_sad_blk_64x64);
+      cpi->src_sad_blk_64x64 = NULL;
+    }
+  }
   // Check for dynamic resize, for single spatial layer for now.
   // For temporal layers only check on base temporal layer.
   if (cpi->oxcf.resize_cfg.resize_mode == RESIZE_DYNAMIC) {

av1/encoder/ratectrl.h

diff --git a/av1/encoder/ratectrl.h b/av1/encoder/ratectrl.h
index df177b9..9bb6ca1 100644
--- a/av1/encoder/ratectrl.h
+++ b/av1/encoder/ratectrl.h
@@ -256,6 +256,9 @@
   int frame_level_fast_extra_bits;
 
   double frame_level_rate_correction_factors[RATE_FACTOR_LEVELS];
+
+  int prev_coded_width;
+  int prev_coded_height;
   /*!\endcond */
 } RATE_CONTROL;