No, it is not a virus / malware.
You say it only appears when you open Firefox, there is possibly no malware behind this.
I also have this svchost process running LocalServiceAndNoImpersonation and this PC is clean.
So far LocalServiceAndNoImpersonation is a legit process and is used by Windows AppLocker.
Windows AppLocker is a security feature of Windows.
https://technet.microsoft.com/en-us/library/dd759117.aspx
AppLocker is a new feature in Windows 7 and Windows Server 2008 R2 that allows you to specify which users or groups can run particular applications in your organization based on unique identities of files. If you use AppLocker, you can create rules to allow or deny applications from running.
You can inspect it with ProcessExplorer.
https://technet.microsoft.com/sysinternals/bb896653
There should be also the loaded DLL mentioned.
http://www.bleepingcomputer.com/startups/appidsvc.dll-25613.html
A Microsoft Service that is used by AppLocker to determine and verify the identity of an applicaiton. Please note that this service is launched by svchost.exe, but the actual application is what is listed as the filename.