Try to reduce flicker further in live development with node server

[joelrbrandt]

cc @njx @gruehle

I think the stuff we did in #2982 reduces the flicker enough for shipping in sprint 21. However, we might be able to do better with some more intelligent cache control and a better understanding of when window.reload does and doesn't ignore cache data.

Assigning this to myself to characterize this better as part of sprint 22.

[pthiess]

Reviewed - thanks for your self-assignment, Joel :)

[njx]

Moving to sprint 23 since @joelrbrandt is tied up this sprint and it's not an urgent issue to address.

[pthiess]

Removed the milestone sprint 23 as we're not having bandwidth.