Dynamic method calls in Queue.ts could fail with minification

[jeffposnick]

There are some dynamic method calls in Queue.ts along the lines of:

workbox/packages/workbox-background-sync/src/Queue.ts

Line 279 in 48f53f7

await this._queueStore[`${operation}Entry`](entry);

(and a few more similar ones).

These method calls can fail if minification changes the names of the methods on the underlying QueueStore object.

I think it might be possible (via declare in TypeScript?) to give hints to various minifiers that they shouldn't do renaming, but honestly it might be easier just to use if()/else() conditionals to find the right method name to call, since there are usually only a couple to choose from for each code path.