Issue 598780  has been merged into this issue.

Fixed by cl/119117027.

Unless you have not pushed this to production yet - this is not fixed, I still do not get results.

What are you trying exactly?

Searching for "data_" on cs.chromium.org should now redirect you to https://cs.chromium.org/#search/&q=data_&sq=package:chromium&type=cs - the important part is the "sq=package:chromium" that was missing from the URL before.

See the thread -
https://groups.google.com/a/chromium.org/d/msg/infra-dev/KhJh-h_D0Vc/tzZrbtl3GQAJ
I noted that it was missing from the URL, but it still worked for Aaron from the Chrome team and not for me, which is why it was suggested that I file an issue.

Unless Aaron can no longer get results from that URL - there is still something different between us and there should not be.

Yep, sorry, there was some more internal discussion on that CL.
Due to various legacy reasons these search requests make a request that looks like:

https://cs.chromium.org/p/cs/codesearch/codesearch/json?search_request=b&query=foo+package%3Achromium&max_num_results=11&results_offset=0&exhaustive=false&return_snippets=true&return_all_snippets=false&return_line_matches=false&sort_results=false&lines_context=1&return_directories=true&return_local_augmented_results=true&return_decorated_snippets=true&full_history_search=false&internal_options=b&debug_level=0&consolidated_query=true&internal_options=e&search_request=e&sid=1459923082314&

Those internal_options=b&debug_level=0&consolidated_query=true&internal_options=e params set some internal options (debug_level and consolidated_query) on the search request, but they're applied *only if you're coming from an internal Google IP address*.  consolidated_query tells the backend to search across *all* packages and disregard any package:... you may or may not have put in the search query.  So that's why the searches worked just fine for Aaron and the Chrome team.

So the fix was to always set package:chromium.

I figured it was something like that.
Thank you for the explanation!