Add Spdy4Experiment group.

Add Spdy4Experiment group.

Add Spdy4Experiment group which can be kept at the same size as Spdy4Control,
while Spdy4Enabled can be arbitrary.  This allows enabling SPDY/4 on more than
50% while having a group the same size as Spdy4Control for convenient
comparison.

BUG=428690
Committed: https://crrev.com/e3553d92bfbf3a257aaf2982e44ecd098ec1353e
Cr-Commit-Position: refs/heads/master@{#302171}

[Bence, 2014-10-30 17:08:27]

bnc@chromium.org changed reviewers:
+ rch@chromium.org

[Bence, 2014-10-30 17:08:27]

Ryan: PTAL.  Thanks.

[Ryan Hamilton, 2014-10-30 17:34:32]

https://codereview.chromium.org/689923002/diff/1/chrome/browser/io_thread.cc
File chrome/browser/io_thread.cc (right):

https://codereview.chromium.org/689923002/diff/1/chrome/browser/io_thread.cc#...
chrome/browser/io_thread.cc:845: } else if (spdy_trial_group ==
kSpdyFieldTrialSpdy4GroupName) {
We've been doing a lot of finch config work with QUIC lately. An alternative is
to do something like:

if (spdy_trail_group.starts_with(kSpdyFieldTrialSpdy4GroupName) {
  ..
}

Then you can create an unlimited number of different group names without needing
to change the code.  The other thing you could consider would be do something
like we do with QUIC where we make use of params in each field trial group to
control various knobs explicitly, instead of needing to look at/parse out the
group name.

I think it would be better to pursue one of these approaches rather than
hardcoding a new group name in the code.

What do you think?

[Bence, 2014-10-30 17:50:19]

Patchset #2 (id:20001) has been deleted

[Bence, 2014-10-30 17:53:29]

Patchset #2 (id:40001) has been deleted

[Bence, 2014-10-30 18:39:03]

Ryan: PTAL.

https://codereview.chromium.org/689923002/diff/1/chrome/browser/io_thread.cc
File chrome/browser/io_thread.cc (right):

https://codereview.chromium.org/689923002/diff/1/chrome/browser/io_thread.cc#...
chrome/browser/io_thread.cc:845: } else if (spdy_trial_group ==
kSpdyFieldTrialSpdy4GroupName) {
This is a great idea.  I am extenting this to SpdyDisabled, and adding
Spdy31Enabled.  This will allow us to deprecate *Control*, and have a clearer
group layout, like:
* SpdyDisabled-5
* Spdy31Enabled-5
* Spdy4Enabled-5
* Spdy4Enabled-rest

[Ryan Hamilton, 2014-10-30 21:33:32]

lgtm, modulo a suggestion for a followup.

https://codereview.chromium.org/689923002/diff/60001/chrome/browser/io_thread.cc
File chrome/browser/io_thread.cc (right):

https://codereview.chromium.org/689923002/diff/60001/chrome/browser/io_thread...
chrome/browser/io_thread.cc:854: } else if (spdy_trial_group ==
kSpdyFieldTrialSpdy4ControlGroupName) {
If you named the spdy/4 control group as:

Spdy31EnabledAsSpdy4ControlGroup, then you could avoid this "else if" block
altogether.

If you make this change in finch after this CL lands, you could then land a
followup removing this block.

[Ryan Hamilton, 2014-10-30 21:34:12]

On Thu, Oct 30, 2014 at 11:39 AM, <bnc@chromium.org> wrote:

> This will allow us to deprecate *Control*, and have a
> clearer group layout, like:
>

​Oh, I think you suggested what I just suggested. WHoops! Yes, I totally
agree with *your* suggestion :>​

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[Bence, 2014-10-30 21:45:16]

The CQ bit was checked by bnc@chromium.org

[commit-bot: I haz the power, 2014-10-30 21:46:15]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/689923002/60001

[commit-bot: I haz the power, 2014-10-30 22:29:58]

Committed patchset #2 (id:60001)

[commit-bot: I haz the power, 2014-10-30 22:30:40]

Patchset 2 (id:??) landed as
https://crrev.com/e3553d92bfbf3a257aaf2982e44ecd098ec1353e
Cr-Commit-Position: refs/heads/master@{#302171}