Add support for Android User List in Trace Processor

[annathedroid]

This change introduces the ability to parse, store, and query Android user list information from Perfetto traces.

Previously, information about the different Android users (e.g., system, secondary, guest) present on the device was not extracted from the trace. This change adds the necessary logic to process the AndroidUserList trace packet.

Key changes include:

• New Table: Added a table __intrinsic_user_list to store the user ID (uid) and user type (type).
• Proto Parsing: Implemented parsing logic within AndroidProbesModule to handle the AndroidUserList message and populate the new table.
• SQL View: Exposed the data through a new Perfetto SQL view named android_users, with columns uid and type.
• Error Handling: Added stats::user_list_errors to track any issues during parsing.
• Testing: Included a new diff test (test_ftrace_user_list) using a dedicated trace file (trace_user_list.pftrace) to validate the end-to-end functionality of parsing and querying the android_users view.

These changes enable trace analysts to easily query and correlate trace events with specific Android users on the system.

[aMayzner]

LGTM to me!

[primiano]

Removing myself and Ryan, Anna or Lalit (just one of the two) are the best candidates to review this

[LalitMaganti]

I think I also asked about this but how does this correspond to uid on the android_process_metadata [1] table.

I think just calling this uid and "android user id" is highly confusing for everyone. I would like to see a explanation of this somewhere.

[1] https://source.chromium.org/chromium/chromium/src/+/main:third_party/angle/third_party/perfetto/src/trace_processor/perfetto_sql/stdlib/android/process_metadata.sql;l=78?q=android_process_metadata&ss=chromium

[LalitMaganti]

On android_process_metada, I also see user_id as a column and says it is for "multi-user devices". How does that factor into things?

[annathedroid]

I can change it to android_user_id because it is exactly that in processes.

[annathedroid]

in android_process_metadata

linux uid = user_id * 1000 + uid (android app id)

bear in mind uid which is shown by linux ps is not present in android_process_metadata and android app id is called uid

[LalitMaganti]

Yeah this is a historical mistake. It's too late to change this now beyond adding some documentation there. We should have done a better job on this when we first designed that table.

[annathedroid]

we can name it user_id to keep the same name in tables