Webcam demo style

[jimbojw]

Implemented a glow to highlight the selected/predicted button both during collection and during game play.

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This change is 

[googlebot]

So there's good news and bad news.

👍 The good news is that everyone that needs to sign a CLA (the pull request submitter and all commit authors) have done so. Everything is all good there.

😕 The bad news is that it appears that one or more commits were authored or co-authored by someone other than the pull request submitter. We need to confirm that all authors are ok with their commits being contributed to this project. Please have them confirm that here in the pull request.

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[nsthorat]

Thanks Jimbo!!

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Review status: 0 of 3 files reviewed at latest revision, all discussions resolved.

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Comments from Reviewable

[dsmilkov]

Thank you!

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Reviewed 2 of 3 files at r2, 1 of 1 files at r3.
Review status: all files reviewed at latest revision, all discussions resolved.

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Comments from Reviewable