Bugfix: Handle seekhead for cues on mkv files.

[fire-light42]

Closes #1143

This fixes the issue with non seekable mkv files, by checking the SEEK_HEAD, as media3 does not currently use SEEK_HEAD at all. A test was also added showing a non seekable mkv file, this was generated by mkvpropedit sample.mkv --chapters large_chapters.xml.

This means that when we parse an MKV file what really happens is:

    find KaxSeekHead
    seek to KaxSeekHead position
    find KaxCues
    seek to KaxCues position
    parse cues
    seek back from KaxCues
    seek back from KaxSeekHead
    parse rest normally

What happened before was:

    find KaxCues <- this step fails
    seek to KaxCues position
    parse cues
    seek back from KaxCues
    parse rest normally

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[fire-light42]

@icbaker

[icbaker]

Please sign the CLA and then we can take a look.

[fire-light42]

Please sign the CLA and then we can take a look.

I cant sign it because I do not have a google account, nor am I interested in creating one. Is there any way to sign it without creating a google account?

[icbaker]

Is there any way to sign it without creating a google account?

Doesn't look like it. From https://cla.developers.google.com/about:

Can I sign the Google CLA without a Google account?

A Google account is required to sign the CLA. Google accounts are used to link individual and corporate CLAs to covered contributors and provide authentication for CLA management.

[fire-light42]

@KingLucius

[fire-light42]

#2268