The following methods are no longer available on the CRM 2015, so please review the code before migrate to CRM 2015 or when planning to upgrade to CRM 2015.
getAuthenticationHeader This method supported use of the Microsoft Dynamics CRM 4.0 web services, which no longer exist.
getServerUrl This method was replaced by getClientUrl.
isOutlookClient This method was replaced by client.getClient
isOutlookOnline This method was replaced by client.getClientState
More information on client-side context properties, please go to: https://msdn.microsoft.com/en-us/library/gg334511.aspx#BKMK_removedmethods