core-list-dart very slow during mutation

[Andersmholmgren]

I thought I was running into the performance issues that are supposed to be fixed in googlearchive/core-list#30 but then I realised that core-list-dart is a separate (at least partially) implementation so this might not be fixed by the js fixes to core-list.

I'm printing out when the observe event to change the data that the list is looking at arrives and there is a noticeable delay between when this prints and the ui updates. This delay gets longer and longer as the list grows.

The change I'm doing is simply moving an item from the top to bottom (or vice versa). i.e. a delete and insert.

This is already like a second or so for a list of around 40 items!!!

[jakemac53]

We port over these changes every time we upgrade all the elements, which we currently do at every official release. If you would like to get these updates quicker and are willing to put a pull request together that would be greatly appreciated, and we would be willing to review and merge it outside of the normal schedule :).

Interestingly I actually see a 0.4.2 tag in the polymer repo.... but not an official release notice. I will see if I can figure out what the situation is there but my guess is that it means a release is pending.

[geppy]

The referenced changes have already been ported.