Disable uploading on ESR

[ghost]

Firefox 60 is an ESR. To avoid problems down the line, we'd like to disable the ability to save screenshots to our servers on ESR releases (note: just ESR, not plain Firefox 60). The screenshots functionality will still be there, but the Save button will be omitted.

From our discussion:

• We should add a pref to do this and convert our current disable-save-button logic to use it
• Add ESR detection to flip the pref
• Add the pref to our documentation and/or SUMO

[jaredhirsch]

We can detect ESR-hood via AppConstants.MOZ_UPDATE_CHANNEL == 'esr'. No need to set a pref.

[ianb]

It feels like the pref is generally useful (especially given the enterprise policy stuff that's being deployed). The reason given that some people/admins want to disable Screenshots is specifically to disable uploading of data (e.g., for computers subject to HIPAA).

[jaredhirsch]

Are you thinking of a separate pref to just disable uploads, like extensions.screenshots.upload-disabled? If so, maybe that could be a separate bug.

I'm proposing that uploads always be disabled if a Firefox is on the ESR channel, which seems like the goal of this bug.

[jaredhirsch]

Ah, the pref is mentioned explicitly in the description for this bug, so I'll just add it 👍