Now that "Activity" is gone from Safari, how do I find and download a streaming flv file on a Mac?
You can see still browse resources in the web inspector.



To download a file, you can copy the URL from the right sidebar, paste it on the location bar, and press ⌥↩.

The web inspector can be shown by pressing ⌥⌘I if you've enabled showing the develop menu in the advanced preferences.