Cleanup: Move flatten-trie to loader.
https://bugs.webkit.org/show_bug.cgi?id=112196

Reviewed by Dirk Pranke.

flatten-trie is used only by the loader, so move it there and make it
private, rather than global in dashbaord_base. Moved the corresponding
unit test from flakiness_dashboard_unittests to loader_unittests.

* TestResultServer/static-dashboards/dashboard_base.js:
* TestResultServer/static-dashboards/flakiness_dashboard_unittests.js:
* TestResultServer/static-dashboards/loader.js:
(.):
* TestResultServer/static-dashboards/loader_unittests.js:


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@145679 268f45cc-cd09-0410-ab3c-d52691b4dbfc