#1476 issue. Updated the function call(`getCodeFromPlayground`) in
`save-playground.js` file from `pagehide` event to change event in ace
editor.
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Co-authored-by: Martin Geisler <mgeisler@google.com>
The embedded Playground's code reset when you navigate between slides.
This has caused problems: if people navigate away from a slide to look
something up, they've suddenly lost their work.
