message: Add docstring to perf_builder()
  Cr-Commit-Position: refs/heads/main@{#38042}
diff: @@ -619,6 +619,17 @@ def try_builder(
  )
  def perf_builder(name, perf_cat, **kwargs):
  + """Add a perf builder.
  +
  + Args:
  + name: builder name (str).
  + perf_cat: the category + name for the /perf/ console, or None to omit from the console.
  + **kwargs: Pass on to webrtc_builder / luci.builder.
  + Returns:
  + A luci.builder.
  +
  + Notifications are also disabled.
  + """
  add_milo(name, {"perf": perf_cat})
  properties = make_goma_properties()
  properties["builder_group"] = "client.webrtc.perf"
  