Add very basic 1-up HTML renderer support

Summary:

• Add a query parameter to select the diff renderer.
• When we populate diffs, use the 1-up renderer if the device isn't a desktop. Don't switch renderers once the page has loaded since it will be a tremendous mess. We can add an "always use 1-up" preference later.
• Tweak JX.Device so we avoid a race condition, where JX.Device.getDevice() may not be valid when other behaviors run.
• Implement enough of the 1-up HTML renderer to provide a vague hint that it actually works.
• Fix a couple of bugs with primitive construction.

Test Plan:
{F29168}
{F29169}

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T2009

Differential Revision: https://secure.phabricator.com/D4423