New flakiness dashboard should align results by revision numbers

New flakiness dashboard should align results by revision numbers
https://bugs.webkit.org/show_bug.cgi?id=123129

Reviewed by Tim Horton.

* include/config.json: Specify the default cache time to be 10 minutes.
* include/json-shared.php: Added Expires and Cache-Control headers. It's configurable via config.json.
* index.html:
(TestResultsView._createResultCell): Don't put '-' in a result cell without time.
(TestResultsView._populateTestPane): Create an array of build times ordered from the newest to the oldest.
Not that build.time() is the newest commit time among all repository for each result. e.g. if we had
both WebKit and Safari repository information in a given result, the newer of the two will be used.
(TestResultsView._createTestResultHeader): Added.
(TestResultsView._createBuildsAndComputeSlownessOfResults): Extracted from _createTestResultRow so
that _populateTestPane could use Build object before calling _createTestResultRow.
(TestResultsView._createTestResultRow): Takes buildTimes. Insert an empty cell for a build time if
the current row doesn't contain that a result for that build time.
(TestResultsView._populateBuilderPane):
* main.css: Tweaked the style so that bubbles are aligned vertically without '-'.
(.resultsTable):
(.resultsTable thead th):
(.resultsTable .resultCell):
(.resultsTable a):
(.resultsTable span a):

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@157772 268f45cc-cd09-0410-ab3c-d52691b4dbfc