Many enterprises rely on policy-installed extensions to enforce restrictions on their devices. But we currently just make a best-effort attempt to install them and do not take any actions if we are unable to install.

Step 1 is to add some UMA stats for "number of policy-installed extensions not loaded" so we can understand the scope of the problem.

Step 2 is to investigate a few safe places (example: corrupted extension that can't be repaired) to force-exit the session.

Step 3 is to decide what next steps should be if we just can't install an extension (not due to corruption - we just can't install it). We could surface this in CPanel, or force-exit the session, but we have to be careful here about force-exiting sessions until we have the stats from step #1, because there may be many enterprises with policy-installed extensions that cannot be installed (example: extensions that are no longer available on the chrome web store, temporary outages of the CWS [what is their SLA?], errors in the configuration [invalid URL specified for an off-store extension], etc).

Raising this issue here so PM can decide how/whether to prioritize this work - we should probably at least do #1 for M59 to scope the problem.