Apple's annual developer conference in San Francisco.
iPhone 6 Front Panel Survives Limited Bending Test
The title of Dickson's video mentions sapphire, but there does not appear to be any confirmation that the part is indeed made of the material. The iPhone 6 has been rumored to be adopting a sapphire crystal display cover for increased durability and scratch resistance, but none of the front panel part leaked seen so far have been confirmed to be made of sapphire.
Apple currently uses Corning's Gorilla Glass as the iPhone display cover, and Corning has argued that Gorilla Glass offers a number of benefits over sapphire, including better resistance to breakage. Some rumors have suggested that sapphire may only used on the 5.5-inch iPhone 6, so the smaller 4.7-inch model may still include a Gorilla Glass display.
Update 8:18 AM: Dickson has now posted the remainder of the video showing hands-on measurements of the part and comparison to the iPhone 5s.