Wherever FindIt gets build URLs, master, builder and build number should be there too. Where does FindIt gets build URLs from?

1. From user input (less often, mostly for ourself to test), copy & paste a url to a failed build is convenient than selecting master/builder and paste a build number IMHO.
2. From SoM, but just the master url.
3. Also used to be from chromium-try-flakes, but CTF is not working now. So out of scope I think.

1) looks like FindIt is willing to accept non-structure input for the sake of good UX. Then, IMO, that UI and only that UI should have the logic for parsing unstructured input. The rest of the FindIt should deal with structured data 
2) sounds like SoM API should be improved, so that FindIt gets more structured response

That makes sense, and thanks for the suggestions!

just think of another one:
4) after a try-job started, buildbucket also returns a build url.

yes, buildbucket returns build URL, but it also returns master, builder, and build number in "build_address" tag for LUCI builds. The format of build_address is "bucket/builder/build_number" or in future "project/bucket/builder/build_number"

Chan: you are working on this already, right?