measurement-sets API can incorrectly order points with OS version without commit...

measurement-sets API can incorrectly order points with OS version without commit time
https://bugs.webkit.org/show_bug.cgi?id=167227

Reviewed by Chris Dumez.

Ignore revision_order for the purpose of ordering data points in /api/measurement-sets.

These orderings are used in some UI (e.g A/B testing) to order OS build numbers which do not have a timestamp
associated with each "revision".

The baseline measurements made in our internal dashboard were using these ordering numbers before ordering
results with build time. Because those data points don't have an associated Webkit revisions, all data points
were ordered first by macOS's revision_order, then build time. Because v3 UI completely ignores revision_order
for the purpose of plotting data points, this resulted in some data points being plotted in a wrong order
with some lines going backwards in time.

This patch addresses this discrepancy by stop ordering data points with revision_order in the JSON API.

* public/api/measurement-set.php:
(MeasurementSetFetcher::execute_query): Fixed the bug.
* server-tests/api-measurement-set-tests.js: Added a test.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@210953 268f45cc-cd09-0410-ab3c-d52691b4dbfc