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

src/applications/differential/controller/DifferentialChangesetViewController.php

@@ -157,6 +157,11 @@ final class DifferentialChangesetViewController extends DifferentialController {
     $parser->setLeftSideCommentMapping($left_source, $left_new);
     $parser->setWhitespaceMode($request->getStr('whitespace'));
 
+    if ($request->getStr('renderer') == '1up') {
+      $parser->setRenderer(new DifferentialChangesetOneUpRenderer());
+    }
+
+
     if ($left && $right) {
       $parser->setOriginals($left, $right);
     }