The colored frame appears with a noticeable delay when you switch the split tabs

[Softvision-CristinaBadescu]

[Affected versions]:

• Nightly 60.0a1
• Tab Split 0.1.9

[Affected Platforms]:

• All Windows
• All Mac
• All Linux

[Prerequisites]:

• Have a clean Firefox profile with the latest Tab Split v0.1.9 installed.
• Have one tab open.

[Steps to reproduce]:

1. Open Firefox browser with the profile from prerequisites.
2. Click the "Tab Split" button.
3. Press "Ctrl/Cmd + Tab" keys combination and observe the behavior.

[Expected result]:

• The other tab is focused and the colored frame appears instantly.

[Actual result]:

• The colored frame takes ~ 1 second to be displayed after the tab is focused.

[Notes]:

• This issue is reproducible regardless of how the tabs are switched.
• Here is a screen recording with this issue: