GitLab

DnsTCPAttempt doesn't handle when read returns 0, which is EOF.
It keeps reading over and over, which will peg the CPU.

Fix it so it stops reading with ERR_CONNECTION_CLOSED,
and add unit tests for both ways the connection can close.

BUG=393923

Review URL: https://codereview.chromium.org/422323004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@287456 0039d316-1c4b-4281-b951-d872f2087c98