Yes, FIFO sounds good, specifically: new suggestions coming in enter the list of Zine suggestions at the top:


[Most recently retrieved snippet]
.
.
.
[Least recently retrieved snippet]


Bonus points: :): if we retrieve suggestions in chunks, it would be awesome to sort them by published date before adding them at the top of the existing list:

Most-recently retrieved snippets {
[Most recently published snippet]
.
.
.
[Least recently published snippet]
}
Previosuly retrieved snippets {
[Most recently published snippet]
.
.
.
[Least recently published snippet]

}

Currently, it's FIFO but the other way around - least recently fetched at the top :)
I'll try to take a look at this next week.

CL just sent out for review.

Side note: It looks like ChromeReader already returns the snippets sorted by publish date, so we get the "bonus points" for free :)

FWIW, I don't think "most recently retrieved" is an optimal way to sort snippets though. It results in snippets lists like this:

Title 1
5 hr. ago

Title 2
10 hr. ago

----- most recent fetch above, previous snippets below

Title 3
5 hr. ago

Title 4
10 hr. ago

I'm aware of that and I think it is the more consistent behavior. As a user, it's frustrating to have to visually parse the entire list again to spot new content, instead it's much easier to rest assured that once you get to the first entry in the list that looks familiar: you're done looking at new stuff.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/dd5aacea530b6a32cb3fdf358093a091d600d08e

commit dd5aacea530b6a32cb3fdf358093a091d600d08e
Author: treib <treib@chromium.org>
Date: Fri Apr 22 09:06:44 2016

[NTP Snippets] Add newly-fetched snippets at the front instead of at the end

BUG= 601736 

Review URL: https://codereview.chromium.org/1908973002

Cr-Commit-Position: refs/heads/master@{#389057}

[modify] https://crrev.com/dd5aacea530b6a32cb3fdf358093a091d600d08e/components/ntp_snippets/ntp_snippets_service.cc
[modify] https://crrev.com/dd5aacea530b6a32cb3fdf358093a091d600d08e/components/ntp_snippets/ntp_snippets_service.h
[modify] https://crrev.com/dd5aacea530b6a32cb3fdf358093a091d600d08e/components/ntp_snippets/ntp_snippets_service_unittest.cc

Proposal from comment #2 implemented.

IMO we might want to re-think this at some point in the future, e.g. order by relevance score rather than recency, but we'll cross that bridge when we get there.