Allow sync-buildbot.js to set a buildbot property only when patches are built

Allow sync-buildbot.js to set a buildbot property only when patches are built
https://bugs.webkit.org/show_bug.cgi?id=172743

Rubber-stamped by Chris Dumez.

Added the ability to specify a buildbot property only when there are build requests to build a patch.

* tools/js/buildbot-syncer.js:
(BuildbotSyncer.prototype.scheduleRequest): Pass in the list of build requests that belong to the same test group.
(BuildbotSyncer.prototype.scheduleRequestInGroupIfAvailable): Ditto.
(BuildbotSyncer.prototype._propertiesForBuildRequest): Added the support for specifying a conditional property.
For the condition type of "built", we check if there was any other
(BuildbotSyncer._parseRepositoryGroup): Added the support for "ifBuilt" conditional.

* tools/js/buildbot-triggerable.js:
(BuildbotTriggerable.prototype._scheduleRequestIfSlaveIsAvailable): Pass in the list of build requests that
belong to the same test group.
(BuildbotTriggerable.prototype._scheduleRequestWithLog): Ditto.

* unit-tests/buildbot-syncer-tests.js:  Added test case for newly added "ifBuilt" as well as specifying a patch.
Updated the various test cases per the addition of new argument to scheduleRequest, _propertiesForBuildRequest,
and scheduleRequestInGroupIfAvailable.
(createSampleBuildRequestWithPatch): Added.

* unit-tests/resources/mock-v3-models.js:
(MockModels.inject): Made "ios-svn-webkit" accept a WebKit patch and roots to allow new testing.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@217623 268f45cc-cd09-0410-ab3c-d52691b4dbfc