DevTools: network emulation: justify profiles.

Remove exuberant items. Specify latency (not used yet).

BUG=245436

Review URL: https://codereview.chromium.org/331223005

git-svn-id: svn://svn.chromium.org/blink/trunk@176612 bbb929c8-8fbe-4397-9dbb-9b2b20218538