GitLab

NESTABLE_ASYNC APIs
(https://codereview.chromium.org/536503002/) to log NetLog
entries in Tracing. This CL is a part of the effort to get
NetLog data into Tracing.

Design Doc:
https://docs.google.com/document/d/1Z2uqj59UEts5IiXX78mkdU4kd6e7kE3JUKPoDK97bVs/edit?usp=sharing

BUG=399701

Review URL: https://codereview.chromium.org/468083004

Cr-Commit-Position: refs/heads/master@{#295089}