Re-enable AVIF grid images.

I completed an audit of the grid image code in libavif. See bug 1114916.

Change-Id: Ifb2d4859bff5fc5647095b04e3bdb4db88a31ae4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2354777Reviewed-by: Peter Kasting <pkasting@chromium.org>
Reviewed-by: Dale Curtis <dalecurtis@chromium.org>
Commit-Queue: Wan-Teh Chang <wtc@google.com>
Cr-Commit-Position: refs/heads/master@{#799413}

third_party/blink/renderer/platform/image-decoders/avif/avif_image_decoder.cc

@@ -588,10 +588,6 @@ bool AVIFImageDecoder::MaybeCreateDemuxer() {
   if (!decoder_)
     return false;
 
-  // TODO(crbug.com/1114916): Disable grid image support in libavif until the
-  // libavif grid image code has been audited.
-  decoder_->disableGridImages = AVIF_TRUE;
-
   // TODO(dalecurtis): This may create a second copy of the media data in
   // memory, which is not great. libavif should provide a read() based API:
   // https://github.com/AOMediaCodec/libavif/issues/11