Adds test coverage for alpine linux

[paulirish]

(redoing this PR against the real upstream)

text from @danbopes:

---

I've gone ahead and added some alpine test coverage using travis-ci and docker to build an alpine image and test the run in there. It may need some tweaks/changes (chromium appears to be in /usr/lib/chrome, but it may not be functionality correctly), but this should be a good start to determine if this is working correctly.

See the following docker test:

See a sample build output of it failing here.

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[danbopes]

I originally committed to his fork, and ultimately wanted him to integrate and continue testing in his environment (As there may have been some bugs with the travis build), to ultimately merge into your repo.

[samccone]

Spent some time digging into this one. Once I saw what tests were failing it became somewhat obvious that there was an issue with any of the tests that actually launch chrome:

  ChromeLauncher:error connect ECONNREFUSED 127.0.0.1:33563 +0ms
  ChromeLauncher:error Logging contents of /tmp/lighthouse.XocAHcn/chrome-err.log +2ms
  ChromeLauncher:error [131:131:0401/180724.977072:ERROR:browser_main_loop.cc(279)] Gtk: cannot open display: :99.0
  ChromeLauncher:error  +0ms

But this was not enough to identify the root issue. By connecting to the docker image and overwriting the entry point to /bin/bash I was able to run the tests and then dump out the error log from chrome:

[100:100:0401/181553.727881:FATAL:zygote_host_impl_linux.cc(107)] No usable sandbox! Update your kernel or see https://chromium.googlesource.com/chromium/src/+/master/docs/linux_suid_sandbox_development.m

So issue #25 strikes again!

[samccone]

After turning the flag off, and giving chrome enough time to launch we are greeted by another fun error message

Failed to move to new namespace: PID namespaces supported, Network namespace supported, but failed: errno = Operation not permitted
[316:316:0401/182733.195220:FATAL:zygote_host_impl_linux.cc(182)] Check failed: ReceiveFixedMessage(fds[0], kZygoteBootMessage, sizeof(kZygoteBootMessage), &boot_pid).

This seems to be due to the fact that I did not run the container as --privileged
jessfraz/dockerfiles#65

Once I added that flag to my docker command I was presented with this remaining error
[67:67:0401/183329.379889:ERROR:browser_main_loop.cc(279)] Gtk: cannot open display: :99.0

Which looks to be due to the fact that I am running the docker image on my mac and am not correctly forwarding my X11 server into my docker image execution
https://www.thegeekstuff.com/2010/06/xhost-cannot-open-display/

[samccone]

Alright spent a few more hours on this, still unable to run this locally, and it is running partially on travis

#101

If any feels like picking this back up, please ping this PR and you can have at it.

Thanks