SnoozeTabs favicon doesn't change to the site's favicon after the tab is focused

[SoftVision-EmilPasca]

[Notes]:

• This issue is most likely to reproduce on sites which use WordPress or BlogSpot CMS.

[Affected versions]:

• Nightly 54.0a1
• Snooze Tabs 1.0.15 (built on 03/02/2017)

[Affected Platforms]:

• All Windows
• All Mac
• All Linux

[Prerequisites]:

• Have a Firefox profile with the latest Snooze Tabs add-on version (1.0.15 -dev, built on 03/02/2017) loaded as a temporary add-on.

[Steps to reproduce]:

1. Open the browser with the profile from prerequisite.
2. Navigate to http://www.cracked.com/ and click on the "SnoozedTabs" button.
3. Pick one of the snoozing options e.g. "Real Soon".
4. Wait until the snoozed tab is brought back.
5. Focus the snoozed tab and observe the favicon.

[Expected result]:

• The SnoozeTabs favicon stops flashing ending with the site's favicon.

[Actual result]:

• The SnoozeTabs favicon remains unchanged.

[Notes]:

• Attached a screen recording of the issue:

[bwinton]

(I could replicate this with cracked.com, and took a quick look, but have no idea what's going on there…)

[smartfonreddit]

Relevant: https://bugzilla.mozilla.org/show_bug.cgi?id=1408794

[waldyrious]

I'm seeing this issue as well, with GitHub links. Example with this issue:

(Note: The interface with the tabs on the sidebar is due to the TreeStyleTab extension, but I don't believe it affects this issue, because the problem doesn't occur with other sites)