Set autoplay gesture override experiment based on finch trial group.

Set autoplay gesture override experiment based on finch trial group.

This CL uses the finch trial group name to set WebKit settings for the android autoplay gesture override experiment.  Most of the code for the experiment itself is in https://codereview.chromium.org/1179223002/ .  The present CL will not build without it.

Summary of the experiment: Our goal is to decide if the requirement for a user gesture can be relaxed on android, to allow some media to autoplay without always requiring the user to interact with it manuall.  The finch experiment will let us try various combinations of heuristics for when to autoplay without a user gesture.  We record metrics based on user behavior, such as "manually started playback", "manually stopped playback", etc.

These options are composible, so we just use the trial group name to specify the options directly.  This lets us try different combinations after we get some initial data from the experiment.

BUG=487345, 402044
Committed: https://crrev.com/6524fa4de84e68577cdfcc405be2f3b5cb167f73
Cr-Commit-Position: refs/heads/master@{#348762}

[liberato (no reviews please), 2015-09-10 21:15:48]

liberato@chromium.org changed reviewers:
+ davidben@chromium.org, wfh@chromium.org

[liberato (no reviews please), 2015-09-10 21:33:24]

liberato@chromium.org changed reviewers:
+ rkaplow@chromium.org

[liberato (no reviews please), 2015-09-10 21:44:35]

Hi all

I'd appreciate it if each of you could provide owner feedback on (at least) the
following files.  alternatively, please refer me to a more appropriate reviewer
if i've picked badly:

davidben@: content/
wfh@: common_param_traits_macros.h
rkaplow@: histograms.xml .

thanks
-fl

[rkaplow, 2015-09-11 21:03:28]

lgtm

histogram lgtm

[Will Harris, 2015-09-11 22:14:23]

content/public/common/common_param_traits_macros.h lgtm

[davidben, 2015-09-11 22:48:52]

lgtm

[liberato (no reviews please), 2015-09-14 17:20:56]

The CQ bit was checked by liberato@chromium.org

[commit-bot: I haz the power, 2015-09-14 17:21:22]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1331203003/40001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1331203003/40001

[commit-bot: I haz the power, 2015-09-14 19:16:23]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-09-14 19:16:24]

Try jobs failed on following builders:
  win_chromium_rel_ng on tryserver.chromium.win (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.win/builders/win_chromium_rel_...)

[liberato (no reviews please), 2015-09-14 22:52:17]

The CQ bit was checked by liberato@chromium.org

[commit-bot: I haz the power, 2015-09-14 22:53:05]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1331203003/40001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1331203003/40001

[commit-bot: I haz the power, 2015-09-14 23:26:16]

Committed patchset #3 (id:40001)

[commit-bot: I haz the power, 2015-09-14 23:27:02]

Patchset 3 (id:??) landed as
https://crrev.com/6524fa4de84e68577cdfcc405be2f3b5cb167f73
Cr-Commit-Position: refs/heads/master@{#348762}

[commit-bot: I haz the power, 2015-09-23 12:38:56]

Patchset 3 (id:??) landed as
https://crrev.com/6524fa4de84e68577cdfcc405be2f3b5cb167f73
Cr-Commit-Position: refs/heads/master@{#348762}