feat: take Firefox support out of beta

[flotwig]

• Closes Take Firefox support out of beta; put firefoxGcInterval behind version switch #8241

User facing changelog

• Firefox support is now out of beta!
• Updated firefoxGcInterval workaround to only apply to versions of Firefox older than 80. A warning will be presented if an older version is used.

Additional details

New warning:

(note, the BrowserIcon for Custom Firefox is wrong (?)... not related to these changes)

How has the user experience changed?

PR Tasks

• Have tests been added/updated?
• Has the original issue been tagged with a release in ZenHub?
• Has a PR for user-facing changes been opened in cypress-documentation? docs: remove Firefox beta status, update firefoxGcInterval docs cypress-documentation#3168
• Have API changes been updated in the type definitions?
• [na] Have new configuration options been added to the cypress.schema.json?

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[cypress]

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Test summary

8529 • 0 • 124 • 3

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Run details

Project	cypress
Status	Passed
Commit	6b0291b
Started	Sep 25, 2020 5:35 PM
Ended	Sep 25, 2020 5:46 PM
Duration	11:26 💡
OS	Linux Debian - 10.2
Browser	Multiple

View run in Cypress Dashboard ➡️

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[kuceb]

we also claim firefox is in beta when we list supported browsers:
other than that looks good

[flotwig]

oo, nice catch, thanks

[flotwig]

wow, our tests really do not like FF 81...

[flotwig]

@bkucera the e2e test failures seem to be related to an issue with video recording and Firefox 80, not specifically related to this PR. I am able to reproduce failures in develop by running 4_domain_spec with Firefox 79 (passes) and Firefox 80 (fails with video recording error from no frames).

4_domain_spec passing on develop by Firefox version:

	headed	headless
Firefox 79.0	✔️	✔️
Firefox 80.0	❌	❌

So for this PR let's not bump the docker image. I'll create a new issue for this.

[flotwig]

@bkucera i've completed testing this PR against the memory leak repro we have in 1_firefox spec. Here are the results + videos running in a Fedora VM with 3GB of RAM:

• Firefox 79 with forced GC disabled - invokes Fedora's OOM killer when system runs out of RAM, as expected
• Firefox 79 - completes in 288 seconds with forced GC happening
• Firefox 80 - completes in 208 seconds with NO forced GC
  • from the debug output (and the fact that it's ~40% faster) you can see that no forced GC is happening

I believe that this confirms that Mozilla fixed the memory leak as of FF 80, and also confirms that this PR still appropriately handles forced GC for older versions of Firefox.

[kuceb]

Looks good