Can you explain how? I don't understand how a hash collision of two PDF files would help with this. Surely if it wanted to download the file at 'https://commondatastorage.googleapis.com/chromium-browser-of..., it would need the actual hash of that specific file?

edit: I just read mbrock's comment above which explained it perfectly. Didn't realize it was testing the url to see if there was an actual update available, I thought it was doing the actual update.