In addition to Bug 1074645 there is another test that fails. https://tbpl.mozilla.org/php/getParsedLog.php?id=49166858&tree=Thunderbird-Trunk#error3 SUMMARY-UNEXPECTED-FAIL | C:\slave\test\build\mozmill\testLocalICS.js | testLocalICS.js::testLocalICS EXCEPTION: Timeout exceeded for waitForElement Lookup: /id("messengerWindow")/id("tabmail-container")/id("tabmail")/id("tabpanelcontainer")/id("calendarTabPanel")/id("calendarContent")/id("calendarDisplayDeck")/id("calendar-view-box")/id("view-deck")/id("day-view")/anon({"anonid":"mainbox"})/anon({"anonid":"scrollbox"})/anon({"anonid":"daybox"})/[0]/anon({"anonid":"boxstack"})/anon({"anonid":"topbox"})/{"flex":"1"}/{"flex":"1"}/{"flex":"1"}/{"tooltip":"itemTooltip","calendar":"1412044950439"} at: utils.js line 447 TimeoutError utils.js:447 13 waitFor utils.js:485 1 MozMillController.prototype.waitFor controller.js:685 3 MozMillController.prototype.waitForElement controller.js:699 1 testLocalICS testLocalICS.js:74 1 Runner.prototype.wrapper frame.js:585 9 Runner.prototype._runTestModule frame.js:655 9 Runner.prototype.runTestModule frame.js:701 3 Runner.prototype.runTestFile frame.js:534 3 runTestFile frame.js:713 3 Bridge.prototype._execFunction server.js:179 10 Bridge.prototype.execFunction server.js:183 16 Session.prototype.receive server.js:283 3 AsyncRead.prototype.onDataAvailable server.js:88 3 TEST-UNEXPECTED-FAIL | (runtestlist.py) | Exited with code 1 during directory run

This seems to be caused by the same error as noted in Bug 1074645, marking as duplicate.