STR:

1. Open https://pad.mozilla.org/p/7LVooPJ3OM (note: Mozilla auth required. This will not reproduce with the public instance of etherpad)
2. Zoom the page by using Ctrl+mouse wheel to, say, 150%.
3. Switch to another tab
4. Switch back to the etherpad tab

Expected results:
Page zoom is preserved

Actual results:
Page zoom is reset to 100%.

I asked others on slack to reproduce this but they couldn't so it's possibly at least Windows specific.

I could not reproduce with beta but I could reproduce with a fresh profile in Nightly so I don't believe it is profile / extension related.

I can reproduce with Firefox Developer Edition (70.0b1), also on Windows.

Is this a regression?

Hello! Here is the regression range made using Windows 10x64:

Last good revision: 91c42888cf7fa67f2b9d08d0e62cb203ad1e6619
First bad revision: 70e7c3ef6cae2266147c38ad250692ffe84aec26
INFO: Pushlog:
https://hg.mozilla.org/mozilla-central/pushloghtml?fromchange=91c42888cf7fa67f2b9d08d0e62cb203ad1e6619&tochange=70e7c3ef6cae2266147c38ad250692ffe84aec26

If more information is needed please let me know. Thank you!

[Tracking Requested - why for this release]:
We shouldn't ship this.

https://hg.mozilla.org/mozilla-central/rev/2bdd2503fbdb

Hi Neil, is this ready for a Beta approval request?

Comment on attachment 9091412 [details]
Bug 1577388, use the top browser when receiving zoom messages, r=mconley

Beta/Release Uplift Approval Request

• User impact if declined: Zoom level gets reset on some pages when switching to another tab and back. Automated test has not yet been made.
• Is this code covered by automated tests?: No
• Has the fix been verified in Nightly?: Yes
• Needs manual test from QE?: Yes
• If yes, steps to reproduce: Steps are listed in bug.
• List of other uplifts needed: None
• Risk to taking this patch: Low
• Why is the change risky/not risky? (and alternatives if risky): None
• String changes made/needed: None

Comment on attachment 9091412 [details]
Bug 1577388, use the top browser when receiving zoom messages, r=mconley

Fix for new regression in 70, OK for uplift for beta 70.

https://hg.mozilla.org/releases/mozilla-beta/rev/eacb80079f3b

Hello,
Reproduced the issue with Firefox 70.0a1 (20190828214452) on Windows 10x64.
The issue is verified fixed with Firefox 71.0a1 (20190916155843) and Firefox 70.0b7 (20190916074538) on Windows 10x64. Etherpad page zoom is kept after switching to another tab and back.