webcodecs: Destroy frames during encoder reset

Bug: 1155724
Change-Id: Icf0a258854ca518596c4b48a9b67bcfec9ec0928
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2596834
Auto-Submit: Eugene Zemtsov <eugene@chromium.org>
Commit-Queue: Thomas Guilbert <tguilbert@chromium.org>
Reviewed-by: Thomas Guilbert <tguilbert@chromium.org>
Cr-Commit-Position: refs/heads/master@{#838159}

third_party/blink/renderer/modules/webcodecs/video_encoder.cc

@@ -505,6 +505,8 @@ void VideoEncoder::ResetInternal() {
     DCHECK(pending_req);
     if (pending_req->resolver)
       pending_req->resolver.Release()->Resolve();
+    if (pending_req->frame)
+      pending_req->frame.Release()->destroy();
   }
   stall_request_processing_ = false;
 }