Thanks to Larry Gray for pointing out that the new version of Adobe Camera RAW (ACR) has a nifty new feature called "Boundary Warp". Previously, you had to crop out much of the edges on a panorama after using the Photos-Merge-Panoramic feature, losing some detail. With Boundry Warp, you can use the Boundary Warp slider fill in the entire frame. This process will cause some distortion but that can be fixed.
In the tutorial to the right Russell Brown walks you through the process of using Boundry Warp. Notice that Russell is doing the tutorial in ACR which is how it would look when doing Boundry Warp in Photoshop but the interface looks virtually identical in
Lightroom 6.4/Lightroom cc 2015.4 because of course ACR is built into Lightroom.
This feature is extremely handy if you shoot panoramas and stitch them together with Photomerge feature in Lightroom/ACR like many real estate photographers do.
Update Feb 13: John Driggers has confirmed that Boundary Warp is NOT in Lightroom 6.4 since ACR 9.1.1 is the last version of ACR available for the non-CC version of Lightroom. Actually Adobe announced some time ago that ACR 9.1.1 would be the last version of ACR available for Lightroom CS6.