1397207 - Specific websites (http/s redirects) are still displayed in the "Top Sites" after they are dismissed from the context menu

Status: NEW

(Firefox :: New Tab Page, defect, P3)

Description

[Marius Coman [:mcoman], Ecosystem QA - PTO until 8th of November, for any requests ping :cmuresan]

Attachment: top sites.gif

Notes:
- The issue is reproducible on the following websites:
		- https://9gag.com/
		- https://wordpress.com/
		- on https://www.facebook.com/ the issue is intermittent.
There may be more websites like this, but I have not found them yet.

Affected versions:
- Firefox: 57.0a1, Build ID: 20170905100117

Affected Platforms:
- All Windows
- All Mac
- All Linux

Prerequisites:
- browser.newtabpage.activity-stream.enabled is set to true in about:config on a clean new profile.

Steps to reproduce:
1. Open the browser with the profile from prerequisites.
2. Navigate to https://9gag.com/ and open a new tab.
3. Close the previous tab and navigate again to https://9gag.com/
4. Repeat step 3 at least 2 more times.
5. Restart the browser.
6. Dismiss the "9Gag" Top Site.
7. Observe the "Top sites" area.

Expected result:
- Only the default top sites are displayed.

Actual result:
- The previously dismissed top site is still displayed.

Additional Notes:
- Attached a screen recording of the issue