Add Picture-in-Picture API methods

[beaufortfrancois]

Description

Following #5824 (comment), this PR adds support for some Picture-in-Picture methods described in the spec and article

Specific Changes proposed

This PR is about entering and leaving Picture-in-Picture in the player. It also makes sure that we can listen to the enterpictureinpicture and leavepictureinpicture events on the player.

Requirements Checklist

• Feature implemented / Bug fixed [Support for picture-in-picture API #5824]
• If necessary, more likely in a feature request than a bug fix
  • Change has been verified in an actual browser (Chome, Firefox, IE)
  • Unit Tests updated or fixed
  • Docs/guides updated
  • Example created (starter template on JSBin)
• Reviewed by Two Core Contributors

[welcome]

💖 Thanks for opening this pull request! 💖

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• Run npm run lint -- --errors locally to catch formatting errors earlier.
• Include tests when adding/changing behavior.
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We get a lot of pull requests on this repo, so please be patient and we will get back to you as soon as we can.

[gkatsev]

Can an "abstract"/empty method be added to tech.js, for example https://github.com/videojs/video.js/blob/master/src/js/tech/tech.js#L767-L772? It's needed because if another tech that doesn't implement this method yet ends up being used (for example videojs-flash), we don't want it to throw an error.

[beaufortfrancois]

Can an "abstract"/empty method be added to tech.js, for example https://github.com/videojs/video.js/blob/master/src/js/tech/tech.js#L767-L772? It's needed because if another tech that doesn't implement this method yet ends up being used (for example videojs-flash), we don't want it to throw an error.

@gkatsev Done in 44d09fc

[gkatsev]

Works great, thanks!

[gkatsev]

We try to have two core contributors review PRs before they're merged but this is definitely on the way! Thanks again!

[beaufortfrancois]

@gkatsev Hopefully it's gonna be OK then. Thanks for reviewing ;)

[gkatsev]

Just realized promises may not be available by default.

[beaufortfrancois]

@gkatsev I think we're good now. WDYT?

[welcome]

Congrats on merging your first pull request! 🎉🎉🎉

[gjanblaszczyk]

@gkatsev Why we need handleFocus here? I thought it should be removed... and this.boundHandleKeyPress_ doesn't exist inside the player class.

[beaufortfrancois]

FYI. This change was not part of my proposed changes.

[gkatsev]

Hm... must've snuck in when I was fixing merge conflicts. I'll make sure that it's fixed in master. Nice find @gjanblaszczyk

[gkatsev]

PR to re-remove them: #6053

[GeoTimber]

Jsut a quick question, how do I disable the picture in picture button from the player init options?

[gkatsev]

@GeoTimber see the option here #6002 (comment)