Danny, is this a legit blocker for today's DEV RC Push?  For just glados?

this should be just blocker for glaods family.

add more info here

example failure link 
https://sponge.corp.google.com/invocations?searchFor=user:chromeos-test+build:caroline-release/R71-11078.0.0+suite:bvt-inline+build_RootFilesystemSize

looks like the available space is shrinking for glados in general, just need to fix the test?  Looking at the history, this test check for free space and continue shrinking  https://cs.corp.google.com/chromeos_public/src/third_party/autotest/files/client/site_tests/build_RootFilesystemSize/build_RootFilesystemSize.py?type=cs&q=build_RootFilesystemSize.py&sq=package:%5Echromeos_public$&g=0&l=1

stainless only show failure for R71-11078.0.0 https://stainless.corp.google.com/search?view=matrix&row=model&col=build&first_date=2018-09-15&last_date=2018-09-21&test=%5Ebuild_RootFilesystemSize&model=%5Ecaroline%24&exclude_cts=true&exclude_not_run=false&exclude_non_release=true&exclude_au=true&exclude_acts=true&exclude_retried=true&exclude_non_production=false

So this build definitely has issue.  I would say noop here since the test passes > 11078.0.0 for caroline, chell

if no objection, i will close this?

This should not block the release, this is just a warning that we are almost out of space on these devices, it should not have any functional impact on the OS behavior. 

The test needs to be more precise. What is the minimal that we need and if the test fail it should automatically failed the build, it's require too much resource to figure this out whenever it happen.