URL: https://hacks.mozilla.org/2019/03/fast-bump-allocated-virtual-doms-with-rust-and-wasm/

Browser / Version: Firefox Mobile 65.0
Operating System: Android 7.0
Tested Another Browser: Yes

Problem type: Design is broken
Description: Scrollable code blocks change height and page layout jumps, when opening/hiding navigation bar
Steps to Reproduce:

• Scroll down to "Incrementing counter example with Dodrio" code block, or below
• scroll up and down to show and hide the address bar
• the code block size changes when address bar opens and closes
• all of the page below moves up and down.
  issue is similar to https://bugzilla.mozilla.org/show_bug.cgi?id=1277712

Reported by @jimbo1qaz

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