Fix Bug 1496167 - Add installation source to addons installed from activitystream

[rpl]

This PR adds an additional telemetryInfo parameter (introduced in Bug 1433334) to the AddonManager.getInstallForURL call (and add an additional assertion in the existing unit test that cover that ActivityStream feature).

This additional telemetryInfo parameter ensures that we can store the original "installation source" and be able to include it into the addonsManager telemetry events related to the addons installed from ActivityStream (e.g. when the addon has been disable/enabled/uninstalled by the users, even across Firefox restarts).

[rpl]

@k88hudson this is the PR that we have discussing about over IRC.

[k88hudson]

@rpl this looks good, is there a manual test step I can try to verify this?

[rpl]

@k88hudson sure, here is an STR to manually verify it:

• trigger the addon installation from ActivityStream (and allow the addon to be installed)
• open about:telemetry#events-tab in a tab
• look for the telemetry events with addonsManager category
• check that the telemetry events has the expected value set on the source in the extra column.

(as a additional verification you may also enable, disable and/or uninstall the addon and then check that the related telemetry events collected also have the expected value on the source extra var).

[k88hudson]

Great, thanks!

This will be exported to mozilla central via our next export bug in the next couple of days.