OpenWPM can't be installed with Firefox 48+ release version

[gunesacar]

Firefox 48+ won't allow unsigned extensions to be installed, with no override through xpinstall.signatures.required preference.

https://wiki.mozilla.org/Add-ons/Extension_Signing#Timeline

An alternative is to use the developer edition for the crawls, which does not require extensions to be signed.

[englehardt]

We can also use unbranded builds as long as we confirm that the only change is branding.

[englehardt]

A second issue with 48+ is e10s compatibility. Our add-on will require a few updates, see:

https://developer.mozilla.org/en-US/Add-ons/SDK/Guides/Multiprocess_Firefox_and_the_SDK

[englehardt]

#152 moved us to FF52. Extension signing and multiprocess requirements don't seem to be an issue yet. The browser just provides a warning that our extension shouldn't be trusted since it isn't signed. e10s is disabled since our extension isn't compatible, but that's fine.

e10s compatibility will be a concern for the next ESR, FF 59. We will need to update to that version by June 26th, 2018, when support is ended for FF 52 ESR (timeline here). Since FF57 drops support for add-on-sdk-based extensions, we will likely need to make a number of changes to continue to use our instrumentation. Let's track those in #148.