GitLab

Miscellaneous edits to the netlog documentation:

* Don't refer to chromium scripts in the manual section; the user may
  not have a chromium checkout
* Fix the script output (the line of output requires --verbose)
* Explain how to clean up the flags file
* Cross-link to the commandline-flags page
* Link to the online netlog viewer, rather than its README file

Bug: 918221
Test: tools/md_browser/md_browser.py
Test: Upload to gerrit > open file > click "gitiles"
Change-Id: Ib2d0027b58266fa39d2c0400567adb3d113cada6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1820090Reviewed-by: Shimi Zhang <ctzsm@chromium.org>
Commit-Queue: Nate Fischer <ntfschr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#699165}