[Cronet] Allow experimenting with Chrome's internal DNS resolver.

[Cronet] Allow experimenting with Chrome's internal DNS resolver.

Enable by adding "AsyncDNS":{"enable":true} to experimental options.
By default fallback to getaddrinfo() is enabled.
Note that this is only for experimentation because:
1. It's never been used in production
2. It's likely not the desired long term solution on
   Android as it does not contribute to the O/S DNS cache.

BUG=545123
Committed: https://crrev.com/e92c4096de6e0b7761e4e97850245948878c0446
Cr-Commit-Position: refs/heads/master@{#364117}

[pauljensen, 2015-12-09 17:12:59]

Description was changed from

==========
[Cronet] Allow experimenting with Chrome's internal DNS resolver.

Enable by adding "AsyncDNS":{"enable":true} to experimental options.
By default fallback to getaddrinfo() is enabled.

BUG=545123
==========

to

==========
[Cronet] Allow experimenting with Chrome's internal DNS resolver.

Enable by adding "AsyncDNS":{"enable":true} to experimental options.
By default fallback to getaddrinfo() is enabled.
Note that this is only for experimentation because:
1. It's never been used in production
2. It's likely not the desired long term solution on
   Android as it does not contribute to the O/S DNS cache.

BUG=545123
==========

[pauljensen, 2015-12-09 17:17:14]

pauljensen@chromium.org changed reviewers:
+ xunjieli@chromium.org

[pauljensen, 2015-12-09 17:17:14]

Helen, PTAL.

I tested with the Cronet sample app and it seems to work.  You can wee the DNS
requests are done in parallel instead of serially (in half the time!):

AsyncDNS not enabled:
11:48:21.458337 IP 100.110.12.106.15936 > google-public-dns-a.google.com.domain:
19912+ AAAA? p55t.com. (26)
11:48:21.580095 IP google-public-dns-a.google.com.domain > 100.110.12.106.15936:
19912 0/1/0 (103)
11:48:21.580772 IP 100.110.12.106.2722 > google-public-dns-a.google.com.domain:
515+ A? p55t.com. (26)
11:48:21.637546 IP google-public-dns-a.google.com.domain > 100.110.12.106.2722:
515 1/0/0 A 98.229.183.189 (42)

AsyncDNS enabled:
11:58:57.973081 IP 100.110.12.106.62682 > google-public-dns-a.google.com.domain:
26268+ A? p55t.com. (26)
11:58:57.974499 IP 100.110.12.106.62101 > google-public-dns-a.google.com.domain:
45855+ AAAA? p55t.com. (26)
11:58:58.062547 IP google-public-dns-a.google.com.domain > 100.110.12.106.62682:
26268 1/0/0 A 98.229.183.189 (42)
11:58:58.075201 IP google-public-dns-a.google.com.domain > 100.110.12.106.62101:
45855 0/1/0 (103)

The unittest also passes.

[xunjieli, 2015-12-09 18:38:37]

This is very cool! Don't have any useful comment. lgtm with nits.

https://codereview.chromium.org/1507253003/diff/20001/components/cronet/url_r...
File components/cronet/url_request_context_config.cc (right):

https://codereview.chromium.org/1507253003/diff/20001/components/cronet/url_r...
components/cronet/url_request_context_config.cc:7: #include "base/basictypes.h"
Since you are already here, could you remove this unused include?

https://codereview.chromium.org/1507253003/diff/20001/components/cronet/url_r...
components/cronet/url_request_context_config.cc:106: DCHECK(false) << "AsyncDNS
experiment requires NetLog.";
nit: include "base/logging.h"
I forgot to do this myself when I added DVLOG in this file.

[pauljensen, 2015-12-09 18:51:30]

https://codereview.chromium.org/1507253003/diff/20001/components/cronet/url_r...
File components/cronet/url_request_context_config.cc (right):

https://codereview.chromium.org/1507253003/diff/20001/components/cronet/url_r...
components/cronet/url_request_context_config.cc:7: #include "base/basictypes.h"
On 2015/12/09 18:38:37, xunjieli wrote:
> Since you are already here, could you remove this unused include?

Done.

https://codereview.chromium.org/1507253003/diff/20001/components/cronet/url_r...
components/cronet/url_request_context_config.cc:106: DCHECK(false) << "AsyncDNS
experiment requires NetLog.";
On 2015/12/09 18:38:37, xunjieli wrote:
> nit: include "base/logging.h"
> I forgot to do this myself when I added DVLOG in this file.

Done.

[pauljensen, 2015-12-09 18:55:04]

The CQ bit was checked by pauljensen@chromium.org

[pauljensen, 2015-12-09 18:55:04]

The patchset sent to the CQ was uploaded after l-g-t-m from
xunjieli@chromium.org
Link to the patchset: https://codereview.chromium.org/1507253003/#ps40001
(title: "address nits")

[commit-bot: I haz the power, 2015-12-09 18:57:01]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1507253003/40001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1507253003/40001

[commit-bot: I haz the power, 2015-12-09 19:13:57]

Description was changed from

==========
[Cronet] Allow experimenting with Chrome's internal DNS resolver.

Enable by adding "AsyncDNS":{"enable":true} to experimental options.
By default fallback to getaddrinfo() is enabled.
Note that this is only for experimentation because:
1. It's never been used in production
2. It's likely not the desired long term solution on
   Android as it does not contribute to the O/S DNS cache.

BUG=545123
==========

to

==========
[Cronet] Allow experimenting with Chrome's internal DNS resolver.

Enable by adding "AsyncDNS":{"enable":true} to experimental options.
By default fallback to getaddrinfo() is enabled.
Note that this is only for experimentation because:
1. It's never been used in production
2. It's likely not the desired long term solution on
   Android as it does not contribute to the O/S DNS cache.

BUG=545123
==========

[commit-bot: I haz the power, 2015-12-09 19:13:58]

Committed patchset #3 (id:40001)

[commit-bot: I haz the power, 2015-12-09 19:15:36]

Description was changed from

==========
[Cronet] Allow experimenting with Chrome's internal DNS resolver.

Enable by adding "AsyncDNS":{"enable":true} to experimental options.
By default fallback to getaddrinfo() is enabled.
Note that this is only for experimentation because:
1. It's never been used in production
2. It's likely not the desired long term solution on
   Android as it does not contribute to the O/S DNS cache.

BUG=545123
==========

to

==========
[Cronet] Allow experimenting with Chrome's internal DNS resolver.

Enable by adding "AsyncDNS":{"enable":true} to experimental options.
By default fallback to getaddrinfo() is enabled.
Note that this is only for experimentation because:
1. It's never been used in production
2. It's likely not the desired long term solution on
   Android as it does not contribute to the O/S DNS cache.

BUG=545123

Committed: https://crrev.com/e92c4096de6e0b7761e4e97850245948878c0446
Cr-Commit-Position: refs/heads/master@{#364117}
==========

[commit-bot: I haz the power, 2015-12-09 19:15:37]

Patchset 3 (id:??) landed as
https://crrev.com/e92c4096de6e0b7761e4e97850245948878c0446
Cr-Commit-Position: refs/heads/master@{#364117}