DO NOT MERGE: Fix Matroska issues

related-to-bug: 3331623

Squashed commit of the following:

commit 8484811f3784564ce962ec1b6311bac532d73ffc
Author: Andreas Huber <andih@google.com>
Date:   Tue Jan 11 11:56:06 2011 -0800

    Properly parse Matroska lacing flags and extract all frames contained in a block.

    related-to-bug: 3331623

commit 38f1f39381a01659577461b3d35bd22db45ba317
Author: Andreas Huber <andih@google.com>
Date:   Mon Nov 15 15:10:34 2010 -0800

    Proper support for variable NALsize lengths of AVC content in .mkv files.

    related-to-bug: 3197442

Change-Id: I4b404f3c3d0a2a2fa336b9edff75eb25ffc66a2f