When updating `src/net/base/registry_controlled_domains/effective_tld_names.dat`:

1. Obtain the new effective_tld_names.dat, probably by downloading
   https://publicsuffix.org/list/public_suffix_list.dat
1. Remove whitespace from the ends of the lines.
   You could possibly use something like:
   ```shell
     sed -i -e "s/\s*$//g" \
         src/net/base/registry_controlled_domains/effective_tld_names.dat
   ```
1. Add the Chromium note back in just after the license at the top, and just
   before '===BEGIN ICANN DOMAINS==='. Ensure there is an empty line above and
   two empty lines below the note. The note should say:
   ```
   // Chromium note: this is based on Mozilla's file:
   // https://publicsuffix.org/list/public_suffix_list.dat
   ```
1. Diff the changes and restore any changes annotated with a `// CHROMIUM`
   comment.
1. Build the `tld_cleanup` target.
1. Run `tld_cleanup` (no arguments needed), typically from `src/out/Default`.
   It will re-generate
   `src/net/base/registry_controlled_domains/effective_tld_names.gperf`.
1. Check in the updated `effective_tld_names.dat`, `effective_tld_names.gperf`.

Note that gperf is no longer used for effective_tld_names, but when building
Chromium, the file `effective_tld_names.gperf` will be parsed by `make_dafsa.py`
to generate the file `effective_tld_names-inc.cc`, which is included in
`registry_controlled_domain.cc`.
