[Backport] Security bug 329674887 (2/2)

Cherry-pick of patch originally reviewed on
https://chromium-review.googlesource.com/c/webm/libvpx/+/5375794:
vp9: fix to integer overflow test

failure for the 16k test: issue introduced
in: c29e637283

Bug: b/329088759, b/329674887, b/329179808

Change-Id: I88e8a36b7f13223997c3006c84aec9cfa48c0bcf
Reviewed-on: https://codereview.qt-project.org/c/qt/qtwebengine-chromium/+/554626
Reviewed-by: Michal Klocek <[email protected]>

Author: marco99zz

chromium/third_party/libvpx/source/libvpx/vp9/encoder/vp9_bitstream.c

@@ -967,7 +967,9 @@ static int encode_tiles_buffer_alloc_size(VP9_COMP *const cpi) {
   const int image_bps =
       (8 + 2 * (8 >> (cm->subsampling_x + cm->subsampling_y))) *
       (1 + (cm->bit_depth > 8));
-  return cpi->oxcf.width * cpi->oxcf.height * image_bps / 8;
+  const int64_t size =
+      (int64_t)cpi->oxcf.width * cpi->oxcf.height * image_bps / 8;
+  return (int)size;
 }
 
 static void encode_tiles_buffer_alloc(VP9_COMP *const cpi) {