Forking from the investigation in  Issue 732927 .
In memory-infra we have a ServiceManagerListener in //services/resource_coordinator/memory_instrumentation/process_map.cc which we use to get the PIDs of the various client processes attached to the memory-infra service.

I added some logging there both to OnServiceCreated and OnServiceStarted and there are two things that are quite odd:
1) I see some services being started but not created (this might be wai depending on the registration order of the listener I guess)
2) Some have PID=0. See logs below, the PID here is the part after the =

OnServiceCreated catalog.[505C0EE9-3013-43C0-82B0-A84F50CF8D84] = 97483
OnServiceCreated content_browser.[505C0EE9-3013-43C0-82B0-A84F50CF8D84] = 97483
OnServiceCreated content_packaged_services.[dbebf790-6d46-47d7-a125-36bcb05ebc5d] = 97483
OnServiceCreated service_manager.[505C0EE9-3013-43C0-82B0-A84F50CF8D84] = 97483

OnServiceStarted content_browser.[fdabe8f3-16b9-460e-aaeb-8704375c2361] = 97483
OnServiceStarted preferences.[fdabe8f3-16b9-460e-aaeb-8704375c2361] = 0
OnServiceStarted content_renderer.3_1[fdabe8f3-16b9-460e-aaeb-8704375c2361] = 97489
OnServiceStarted device.[fdabe8f3-16b9-460e-aaeb-8704375c2361] = 0
OnServiceStarted content_gpu.2[505C0EE9-3013-43C0-82B0-A84F50CF8D84] = 97488
OnServiceStarted content_renderer.4_1[fdabe8f3-16b9-460e-aaeb-8704375c2361] = 97491

Preferences and device have PID 0.
Is this expected?