Fixes flaky HttpServer.SendRaw failures.

While not observed on Linux, running on OSX appears to be much
flakier. Calls to StreamListenSocket::Send are non-blocking writes,
so a single read for multiple writes sometimes did not execute as
expected.

R=rsleevi@chromium.org
BUG=365067

Review URL: https://codereview.chromium.org/245563002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@266647 0039d316-1c4b-4281-b951-d872f2087c98
1 file changed