"Not yet implemented" pop-up appears after removing all Page Shot data

[SoftVision-CosminMuntean]

[Affected versions]:

• Nightly 54.0a1 (Build ID: 20170303030202)
• Page Shot 5.2.6242

[Affected Platforms]:

• All Windows
• All Mac
• All Linux

[Prerequisites]:

• The "xpinstall.signatures.required" is set to "false" and latest Page Shot (5.2.6242) custom build is installed on a new clean profile.
• Have multiple saved shots on the created profile.

[Steps to reproduce]:

1. Open Firefox with the profile from prerequisites.
2. Go to "My Shots" page (https://pageshot.dev.mozaws.net/shots ).
3. From the footer of the page click the "Remove All Data" link.
4. Click the red "Proceed" button.
5. Observe the browser behavior.

[Expected result]:

• All the Page Shot data is deleted and you are redirected to the "Leave Page Shot complete" page.

[Actual result]:

• "Not yet implemented" pop-up is displayed even if all the Page Shot data is deleted.

[Notes:]

• Here is a screen recording with the issue:

[ianb]

We need a product decision on what it should do (#2270), and then revisit this.

[jaredhirsch]

this might also be related to pref-flipping (#2333)

[SoftVision-CosminMuntean]

It seems that this issue is no longer reproducible on the latest Firefox Screenshots (5.2.7676) version. The "Not yet implemented" pop-up is no longer displayed.