Sitecore 8 Bucket

In Sitecore 8 Sitecore.Buckets.Forms.SelectRenderingDatasourceForm is same as that of sitecore 7. The Experience Editor functionality of “Add to here” component using the SelectRenderingDatasource.xml which uses the Sitecore.Buckets.Forms.SelectRenderingDatasourceForm code behind file is working fine. Some of the methods in Sitecore 7 Sitecore.Buckets.Forms.SelectRenderingDatasourceForm are missing in Sitecore 8 but the functionality is working correctly. Are this methods present in some other dll in sitecore 8 where these methods are present. I am currently facing an issue while customizing the SelectRenderingDatasource.xml . How is the backend compatibility maintained?

How is this related to UiPath please ?