1288729 - Wrong message appears when enabling themes if user is signed into Sync

Status: NEW

(Firefox :: Sync, defect, P3)

Description

[Petruta Horea [:phorea], Desktop Test Engineering (back on Sep 5th)]

[Note]:
- This only reproduces if a Firefox account is logged into Sync

[Affected versions]:
- Firefox 48 beta 10
- latest Aurora 49.0a2 (2016-07-21)
- latest Nightly 50.0a1 (2016-07-21)

[Affected platforms]:
- Ubuntu 14.04 64-bit
- Mac OS X 10.10.1
- Windows 7 64-bit

[Steps to reproduce]:
1. Sign in to Sync with an existing account	
2. Install several themes from https://addons.mozilla.org/en-US/firefox/themes/
3. Go to about:addons, Appearance section
4. Select the "Enable" button multiple times for any installed theme

[Expected result]:
- The theme is enabled, there are no notifications visible

[Actual result]:
- "<Theme> will be enabled after you restart Firefox" notification with "Restart now" and "Undo" links is displayed for a short period of time (less than a second)

[Regression range]:
- This issue is not a regression; it reproduces back to Firefox 30.0.