That functionality exists currently using the LEGACY GANTT view, and will be transitioned once all the flash applications are decommissioned. Right now, in your report, go to the "REPORT SETTINGS" and select "SHOW a Special view on the details tab" and select LEGACY GANTT view.
Marty - Interesting! The Workfront Help Desk told me that it could not be done. I just tried what you relayed & I can add it to a dashboard - but it will not pull up - just keeps spinning - showing loading. Do you have one that works for you & pulls up data?
Sounds like a FLASH problem. You need to make sure that you have Flash enabled in your browser. If not sure how, do an internet search on your browser name and enable flash.