Fix render size with !CONFIG_FRAME_SUPERRES

If CONFIG_FRAME_SUPERRES is disabled, and we don't explicitly signal
a render size for a frame, then the render size would be set to the
crop size of the *previous* frame (or 0 for the first frame in a video).

Return to using the VP9 behaviour in this case (albeit coded slightly
differently to help support superres) - ie, use the crop size of the
current frame if an explicit render size is not provided.

We do this by moving the calls to resize_context_buffers() (which sets
up cm->width and cm->height) before the calls to setup_render_size
(which might use those values). Because resize_context_buffers() does not
read any data, the bitstream format should not be affected, aside from
the intended bugfix.

BUG=aomedia:1044

Change-Id: I4fc71b9aea36cc06e10408715c205d9674f87fc2

av1/decoder/decodeframe.c

diff --git a/av1/decoder/decodeframe.c b/av1/decoder/decodeframe.c
index d2e9eac..650a053 100644
--- a/av1/decoder/decodeframe.c
+++ b/av1/decoder/decodeframe.c
@@ -1473,8 +1473,8 @@
 #if CONFIG_FRAME_SUPERRES
   setup_superres(cm, rb, &width, &height);
 #endif  // CONFIG_FRAME_SUPERRES
-  setup_render_size(cm, rb);
   resize_context_buffers(cm, width, height);
+  setup_render_size(cm, rb);
 
   lock_buffer_pool(pool);
   if (aom_realloc_frame_buffer(
@@ -1540,6 +1540,7 @@
 #if CONFIG_FRAME_SUPERRES
       setup_superres(cm, rb, &width, &height);
 #endif  // CONFIG_FRAME_SUPERRES
+      resize_context_buffers(cm, width, height);
       found = 1;
       break;
     }
@@ -1556,6 +1557,7 @@
 #if CONFIG_FRAME_SUPERRES
     setup_superres(cm, rb, &width, &height);
 #endif  // CONFIG_FRAME_SUPERRES
+    resize_context_buffers(cm, width, height);
     setup_render_size(cm, rb);
   }
 
@@ -1584,8 +1586,6 @@
                          "Referenced frame has incompatible color format");
   }
 
-  resize_context_buffers(cm, width, height);
-
   lock_buffer_pool(pool);
   if (aom_realloc_frame_buffer(
           get_frame_new_buffer(cm), cm->width, cm->height, cm->subsampling_x,