Don't `NOTREACHED` when handling malformed CBOR inputs.

Just return `nullopt` and (crucially) set the error code without crashing.

Bug: 879237,884382
Change-Id: I899ceb45648e130d5352a0a487c2d244f41a118d
Reviewed-on: https://chromium-review.googlesource.com/1228938
Commit-Queue: Chris Palmer <palmer@chromium.org>
Reviewed-by: Balazs Engedy <engedy@chromium.org>
Reviewed-by: Tom Sepez <tsepez@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#591854}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 62403b01f1a3edbe0676d4b1f44fa5cb33013006
1 file changed