Bug 1071114 - Tweaking the rocketbar collapsing transition.
Bug 1090562 - [Rocketbar] Implement transitions again r=etienne

Conflicts:
	apps/system/js/app_chrome.js
	apps/system/js/rocketbar.js
	apps/system/test/unit/rocketbar_test.js
Merge pull request #25746 from KevinGrandon/bug_1090562_2_dot_1_uplift

Bug 1090562 - [Rocketbar] Transitions are missing