[Reporting] Make Chromium the default browser

[elasticmachine]

Make chromium the default headless browser choice.

Pre-reqs:

• Reporting API test expansion
• Turn reporting snapshot tests back on (PR)
• Add API and snapshot tests for Chromium (though the snapshot tests are skipped, they will be unskipped when the above PR is checked in)
• Support Chromium in cloud
• Switch to default chromium for segmented cloud users

Note: Phantom should still be the default for CentOS 6.0 and RHEL 6.0 distributions, as those use GLIBC 2.12 and the minimum for Chrome/Chromium is GLIBC 2.14.

[rashmivkulkarni]

@stacey-gammon - can this be moved to 6.3.3 if its not making into 6.3.2 ( FF is tomorrow - July 17)

[stacey-gammon]

cc @epixa @clintongormley Chromium does not work on centos versions < 7.0. According to our support matrix, we support CentOS/RHEL 6.x/7.x. What is the process for removing support for CentOS/RHEL 6.x in v7.0, when we want to completely remove Phantom?

[epixa]

@stacey-gammon Starting a broader discussion is the first step, and I see that you already did that. This is a complicated situation particular because Kibana doesn't currently publish an OS support matrix.

[stacey-gammon]

Closed via #21505