Anca/Test stabilization - multiple tabs navigation

[soncuteanca]

Relevant Links

Bugzilla: 1960042
TestRail: 134647

Description of Code / Doc Changes

• It appears that assertion position checks would sometimes occur during animation states where tab location temporarily moved in unexpected directions before settling in their final positions. The test failed intermittent, but I managed to reproduce it only in headed mode implying timing, rendering issue. Therefore first I've added a custom wait for the scrolling animations to be complete before checking positions. A test diagnosis (by tracking tab positions over milliseconds) showed that when scrolling left, tab X-coordinates actually increase (not decrease), and when scrolling right, they decrease (not increase).

Workflow Checklist

• [ x] Please request reviewers
• If this is an unblocker, please post in Slack.
• If asked to address comments, please resolve conversations.
• If asked to change code, please re-request review from the person who wanted changes.

Thank you!

[vsangereanMOZ]

very nice

[sv-hyacoub]

LGTM

[ben-c-at-moz]

It's fine to merge this, but would you mind making note of the discrepancy between the TestRail TC and the automated test in our channel? I think it might be worthwhile to get Tracy's opinion on that particular matter.]

That said, since the previous test also had that discrepancy, feel free to merge.