Overridden to discard the removed button's viewstate information from the ItemTransactionList if it had been tracking.
If you override this method, you must call base.OnRemoveComplete for the UltraWebToolbar element to continue to work properly.
Target Platforms: Windows 10, Windows 8.1, Windows 8, Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2