Comment 1 for bug 1775719

Code push'd:

http://git.evergreen-ils.org/?p=working/Evergreen.git;a=shortlog;h=refs/heads/user/berick/lp1768947-offline-db-webworkers

This moves the DB access logic into a shared worker. The egLovfield API is unchanged, but all DB reads/writes are now shuttled off to the shared worker.

I also moved the full download block list logic into the web worker since it's so heavy. That way it does not lock the browser up when it's building. Consistent with bug #1727557, I am also displaying an (indeterminate) progress dialog as the block list builds.

As a reminder, shared workers run in their own process, so debugging them means finding the right console logs.

In Chrome, navigate to chrome://inspect/#workers -- Look for the offline-db-worker.js entry and click "Inspect".

In FF, they're under about:debugging#workers

Eyes and testing appreciated. I think I got all the bugs -- the behavior I know to test is working -- but it's big enough others could be lurking.