https://bugs.webkit.org/show_bug.cgi?id=78373

Reviewed by Hajime Morita.

Add TestResult inside a transaction. We use high replication databsae but this should prevent
the duplication in the most of the time.

Also fixed random bugs in Controller and ReportHandler.

* Websites/webkit-perf.appspot.com/controller.py:
(get_persistent_cache):
* Websites/webkit-perf.appspot.com/report_handler.py:
(ReportHandler.post):
* Websites/webkit-perf.appspot.com/report_process_handler.py:
(ReportProcessHandler.post):
(ReportProcessHandler._add_test_if_needed):
(ReportProcessHandler):
(ReportProcessHandler._add_test_result_if_needed):
(ReportProcessHandler._add_test_result_if_needed._float_or_none):
(ReportProcessHandler._add_test_result_if_needed.execute):


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@107531 268f45cc-cd09-0410-ab3c-d52691b4dbfc