This is Longhui stripping bamboo. Pandas are lean mean bamboo processing machines. The keepers put the bamboo in different places in his enclosure so he had to move around to find it. He would plonk himself down by some bamboo, lay almost on his back, strip the leaves off making a mess on his chest then once he's finished he would simply stand up letting the mess fall to the ground then walk to the next pile of bamboo.