Ideally we should use one of these boards for VMTest, instead of Rambi, to also get some Android test coverage early while we are at it.

What's the best representative board for this?

How about caroline?

caroline should be good.

Here is the current default set by the way:

# The default list of pre-cq configs to use.
PRE_CQ_DEFAULT_CONFIGS = [
    'daisy_spring-no-vmtest-pre-cq',  # kernel 3.8 coverage
    'lumpy-no-vmtest-pre-cq',         # kernel 3.8 coverage
    'rambi-pre-cq',                   # vmtest coverage
    'samus-no-vmtest-pre-cq',         # kernel 3.14 coverage
    'whirlwind-no-vmtest-pre-cq',     # brillo coverage
    'x86-alex-no-vmtest-pre-cq',      # x86 coverage
]

ihf are you suggesting swapping out rambi-pre-cq? or just adding caroline?
If simply adding, I'd rather add caroline-no-vmtest-pre-cq; non-vmtest builders are cheap, vmtest ones are not (yet).

(from chromite/lib/constants.py)

Ok, lets swap out but keep rambi as non-vmtest (to not get surprises, and it is a pretty popular config):

+caroline-pre-cq
-rambi-pre-cq 
+rambi-no-vmtest-pre-cq

The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/chromite/+/c12f26a7636ee4e5775cd920a019e2c327d5e4e2

commit c12f26a7636ee4e5775cd920a019e2c327d5e4e2
Author: Aviv Keshet <akeshet@chromium.org>
Date: Sat Feb 25 18:32:08 2017

pre-cq: update default pre-cq; add caroline-pre-cq, demote rambi

Swap in caroline for vmtest instead of rambi. Preserve rambi as
non-vmtest.

BUG= chromium:695638 
TEST=caroline-pre-cq tryjob

Change-Id: I786304bc57768ad060655752a0a769d557d68018
Reviewed-on: https://chromium-review.googlesource.com/446586
Commit-Ready: Aviv Keshet <akeshet@chromium.org>
Tested-by: Aviv Keshet <akeshet@chromium.org>
Reviewed-by: Aviv Keshet <akeshet@chromium.org>

[modify] https://crrev.com/c12f26a7636ee4e5775cd920a019e2c327d5e4e2/lib/constants.py

This looks done, assigning to Aviv to close if true