chore(sysmon): add cache downloader in the proc metric

BUG=b:250926214
test=Ran unit tests

Change-Id: I1002d2d4d006c203b0cccc861ef9ef337d2468c6
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/chromite/+/3947315
Reviewed-by: Allen Li <ayatane@chromium.org>
Commit-Queue: Congbin Guo <guocb@chromium.org>
Auto-Submit: Congbin Guo <guocb@chromium.org>
Tested-by: Congbin Guo <guocb@chromium.org>
diff --git a/scripts/sysmon/proc_metrics_unittest.py b/scripts/sysmon/proc_metrics_unittest.py
index ef3d38e..86f9d55 100644
--- a/scripts/sysmon/proc_metrics_unittest.py
+++ b/scripts/sysmon/proc_metrics_unittest.py
@@ -211,12 +211,17 @@
                         "-credential_file=..."
                     ],
                 ),
+                _mock_process(
+                    name="downloader",
+                    cmdline=["./downloader", "-credential-file", "..."]
+                ),
             ]
             proc_metrics.collect_proc_info()
 
         setter = self.store.set
         calls = []
         calls.extend(_expected_calls_for("autoserv"))
+        calls.extend(_expected_calls_for("cache-downloader"))
         calls.extend(_expected_calls_for("common-tls"))
         calls.extend(_expected_calls_for("curl"))
         calls.extend(_expected_calls_for("dnsmasq"))