I don't want Chrome to crash unless the user's data is at risk otherwise, so no, this isn't expected. :-)

powerd is expected (by Chrome) to be running on a Chrome OS device. It does important things besides turning the screen off (e.g. it's part of the shutdown path). I've documented supported ways to override its behavior at https://www.chromium.org/chromium-os/packages/power_manager in the hopes that people quit stopping its upstart job. :-P

The code to avoid logging an error from OnGetScreenBrightnesPercent was added recently to handle the case where we're running on a VM that doesn't have a backlight (not when powerd isn't running). I think that it probably makes sense to initialize chromeos::StatisticsProvider in ash, since you'd probably want this code to behave similarly there. Do you just need a call to StatisticsProviderImpl::StartLoadingMachineStatistics()?

Yeah. The tricky bit is that we don't have or want content dependencies in ash/mus right now, and there's only a single thread in ash, but StatisticsProviderImpl wants to run on the FILE thread.

I'll take a look at how we could spin up something like a blocking pool. If that seems hard, I'll just reuse FakeStatisticsProvider in ash to keep people moving.

You should feel free to ifdef out that check for ash/mus for now, too.

It turns out that StatisticsProviderImpl launches a tool binary (crossystem) to gather machine information. That's why in runs on the file thread. We don't want to launch that binary twice (once from chrome, once from ash).

So I'm going to wire up FakeStatisticsProvider for now, then later we'll need to sort out some chrome/mash communication to get the data ash needs.

Fixed with the commit below. For some reason bugdroid didn't update this bug.

commit fb20f602654bb390e495835aa5087f98d88143a5
Author: jamescook <jamescook@chromium.org>
Date:   Thu Sep 1 15:34:15 2016 -0700

    mash: Provide a fake chromeos StatisticsProvider in ash
    
    Lower-level code in //chromeos (like the power manager client) assumes it can
    use chromeos::system::StatisticsProvider to determine if it is running in a VM
    (among other things). This is causing CHECK failures on mash when powerd isn't
    running.
    
    For now, provide a fake implementation, since we don't want to create a
    StatisticsProviderImpl in both chrome and ash, as it runs an external binary
    to get its information, and we don't want to do that twice.
    
    BUG= 643289 
    TEST=manual, stop powerd, start chrome on device with --mash, no CHECK failure
    
    Review-Url: https://codereview.chromium.org/2297193007
    Cr-Commit-Position: refs/heads/master@{#416088}