fnTransitionEnd = function () {
				$Ref.off("webkitTransitionEnd transitionend");
				clearTimeout(vTimeout);

				setTimeout(function () {
					fnAnimationCb();
				});
			}
If customHeader is set, this will return the customHeaer. Otherwise it creates a header and put the
title and buttons if needed inside, and finally return this newly create header.
@returns {sap.ui.core.Control|sap.m.Bar} The created header
@protected