Add support for fetching recent builds in Buildbot 0.9 format in BuildbotSyncer

Add support for fetching recent builds in Buildbot 0.9 format in BuildbotSyncer
https://bugs.webkit.org/show_bug.cgi?id=179743

Reviewed by Ryosuke Niwa.

* tools/js/buildbot-syncer.js:
(BuildbotSyncer.prototype._pullRecentBuildsDeprecated): Renamed from _pullRecentBuilds. This method fetch
from Buildbot 0.8 server.
(BuildbotSyncer.prototype._pullRecentBuilds): Method to fetch recent builds from Buildbot 0.9 server.
(BuildbotSyncer.prototype.pathForRecentBuilds): URL for fetching recent builds from Buildbot 0.9 server.
(BuildbotSyncer.prototype.pathForBuildJSONDeprecated): Renamed from pathForBuildJSON.
* unit-tests/buildbot-syncer-tests.js:
(_pullRecentBuilds.it): unit-test - should not fetch recent builds when count is zero.
(_pullRecentBuilds.it): unit-test - should pull the right number of recent builds.
(_pullRecentBuilds.it): unit-test - should handle unexpected error while fetching recent builds.
(_pullRecentBuilds.it): unit-test - should create BuildbotBuildEntry after fetching recent builds.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@228098 268f45cc-cd09-0410-ab3c-d52691b4dbfc