content/browser/resources/traces_internals/README.md

# Trace Report UI

This webui implements chrome://traces, which shows trace reports collected by
background tracing. To test, simply navigating to the URL might be sufficient
if traces are present. If no traces, chrome can be started with a trace config
to force trace collection:

1. Create a new config.pbtxt file anywhere on your desktop.
Copy the config below and save the file.
```
scenarios: {
  scenario_name: "Test"
  trace_config: {
    data_sources: {
      config: {
        name: "org.chromium.trace_event"
        track_event_config: {
          disabled_categories: ["*"],
          enabled_categories: ["toplevel", "__metadata"]
        },
      }
    }
    data_sources: { config: { name: "org.chromium.trace_metadata" } }
  }
  start_rules: {
    name: "Timer Start"
    delay_ms: 0
  }
  upload_rules: {
    name: "Timer End"
    delay_ms: 5000
  }
}
```

2. Then compile the proto with:
```
<outdir>/protoc --encode=perfetto.protos.ChromeFieldTracingConfig \
--proto_path=third_party/perfetto third_party/perfetto/protos/perfetto/config/\
chrome/scenario_config.proto < config.pbtxt > config.pb
```
`config.pbtxt` is the absolute path where your file is on your desktop.
Keep the < > around `config.pbtxt` from the command above.

3. And run chrome with command line:
```
--enable-background-tracing=config.pb
```

You should be able to now collect trace reports on your computer and preview
them on chrome://traces.