Change pub tests and pub local server to use ipV4 localhost by address.

Change pub tests and pub local server to use ipV4 localhost by address.

BUG=dartbug.com/12837
R=ajohnsen@google.com, nweiz@google.com

Committed: https://code.google.com/p/dart/source/detail?r=27880

[Bill Hesse, 2013-09-23 16:13:52]

Here is a fix for the flakiness on the Mac pub test slaves.  We considered other
options, such as sorting the addresses returned from a DNS lookup, but the order
they are returned in is very meaningful, and is specified by an RFC.  It is a
bug in the macos slaves (both kernel 11 and 12, Lion and Mountain Lion), that
they are returning a different order one in 10,000 times.  So we think that, for
the purposes of the tests of pub, using the ipV4 loopback address is best.

I'll be online tonight, if you want to discuss this.
We should add more ipV6 and lookup tests, but that is a separate issue.

[Anders Johnsen, 2013-09-23 16:27:26]

LGTM, but let's be sure we have searched forums and filed a Mac OS X bug before
we mark this issue as resolved.

[nweiz, 2013-09-23 20:03:18]

lgtm

This is gross, but it looks like there's nothing good to do about it on the Dart
side. Can we get dart:io to print a warning if people use localhost in a way
that can trigger this? It would be really easy for users to blunder into this
issue.

[nweiz, 2013-09-23 20:16:59]

Actually, Bob and I want to think about this some more before it gets submitted.
We want to be able to confidently direct users to localhost even if that's not
the address that we bind to in the code. Is that safe right now? If not, what
can we do to make it safe?

[Bill Hesse, 2013-09-25 14:37:04]

Committed patchset #5 manually as r27880 (presubmit successful).

[nweiz, 2013-09-25 19:15:27]

https://codereview.chromium.org/24199004/diff/44001/sdk/lib/_internal/pub/lib...
File sdk/lib/_internal/pub/lib/src/barback/server.dart (right):

https://codereview.chromium.org/24199004/diff/44001/sdk/lib/_internal/pub/lib...
sdk/lib/_internal/pub/lib/src/barback/server.dart:53: .then((server) => new
BarbackServer._(server, barback, rootPackage, host));
Long line.