There's some confusion about the location of this footage. Some say it was taken at Santa Anita race track but others claim the background is definitely Agua Caliente. The latter might be correct because there was a United Artists sales convention in Hollywood in July 1935 and a trip to Agua Caliente was on the itinerary. (Film Daily, July 2, 1935)
The footage of Charlie begins around the :36 mark (Charlie & another man are talking) & lasts about 22 seconds. A large group of Canadian Rotarians were also at the track that day and Charlie is seen in the clip wearing one of their hats.
A caption in the video says Charlie is "Age 44," but he would have actually been 46. His hair, which was quite gray by this time, is dyed black for the filming of Modern Times.