Rethink WalletEventListener.onTransactionConfidenceChanged

[mikehearn]

Originally reported on Google Code with ID 511

Profiling the replay process for Andreas' megawallet shows a surprising amount of time
spent simply iterating transactions in order to call them for this event listener.
The problem is confidence stores the depth and work done rather than recalculate it,
so every transaction is updated for every block. With a lot of transactions, that's
a lot of work per block.

Andreas uses this event for a bunch of things in the UI, for example, as a central
place to trigger recalculation of the list (he adds some throttling on top).

With some tweaks in both bitcoinj and the Android app we can be much smarter about
this and avoid doing lots of useless work.

Reported by hearn@google.com on 2014-01-15 16:22:53

[mikehearn]

dogecoinj hit this problem as well.

Reported by mh.in.england on 2014-03-17 11:31:28

[Giszmo]

We are definitely hitting a brick wall with this one, too. Anybody working on a fix, so we don't have to stumble around, finding the same blockers?

[schildbach]

I'm not aware of anyone working on this.

[schildbach]

I just took a look at this and opened preview PR #1553.