The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/24a358d36c07b62e0037eb130c32518ad1986e5a

commit 24a358d36c07b62e0037eb130c32518ad1986e5a
Author: Michael Spang <spang@chromium.org>
Date: Wed Dec 12 19:55:00 2018

base: fuchsia: Add toplevel trace span for I/O notifications

The message pump is responsible for creating a toplevel span for each time slice
triggered from I/O polling. This type of work is not run in the context of a
a TaskAnnotator, and is completely invisible to tracing without help from the
message pump.

Bug:  914201 
Test: run_content_shell --remote-debugging-port=9222
      ssh root@fuchsia -N -L 9222:localhost:9222
      add localhost to chrome://inspect?tracing & connect

Change-Id: Ib9d248303c1c11d6fd7f616c31e0a76949c14d63
Reviewed-on: https://chromium-review.googlesource.com/c/1373132
Reviewed-by: Nico Weber <thakis@chromium.org>
Reviewed-by: Wez <wez@chromium.org>
Reviewed-by: Sergey Ulanov <sergeyu@chromium.org>
Commit-Queue: Michael Spang <spang@chromium.org>
Cr-Commit-Position: refs/heads/master@{#616005}
[modify] https://crrev.com/24a358d36c07b62e0037eb130c32518ad1986e5a/base/message_loop/message_pump_fuchsia.cc