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- bytes read / written per socket
- total bytes read / written across all sockets

Also changed the Logger class to hold a Log proto instead of individual
fields.

BUG=343228

Review URL: https://codereview.chromium.org/475463002

Cr-Commit-Position: refs/heads/master@{#290009}
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@290009 0039d316-1c4b-4281-b951-d872f2087c98