Enable ScreenOrientation API by default

Enable ScreenOrientation API by default
Add new flag to disable screen orientation locking. Update ScreenOrientationController to be enabled by default, and to check flag state for disabling.

TEST=Set flag to check feature was disabled.
BUG=396760
Committed: https://crrev.com/98fccbf697252ed205523a5ff61de0f402b62b8d
Cr-Commit-Position: refs/heads/master@{#314895}

[jonross, 2015-02-05 16:10:49]

Patchset #1 (id:1) has been deleted

[jonross, 2015-02-05 16:14:05]

Patchset #1 (id:20001) has been deleted

[jonross, 2015-02-05 16:15:36]

jonross@chromium.org changed reviewers:
+ oshima@chromium.org

[jonross, 2015-02-05 16:15:37]

Hi Oshima,

Could you review this change? I'm adding a new flag to disable Screen
Orientation API, as we want it on by default now.

[jonross, 2015-02-05 16:17:09]

jonross@chromium.org changed reviewers:
+ jwd@chromium.org

[jonross, 2015-02-05 16:17:10]

jwd@chromium.org: Please review changes in 

tools/metrics/histograms/histograms.xml

I've updated it to reflect the addition of a new flag.

Thanks,
Jon

[oshima, 2015-02-05 19:02:31]

lgtm

[jwd, 2015-02-05 21:11:56]

lgtm

[jonross, 2015-02-05 21:12:32]

The CQ bit was checked by jonross@chromium.org

[commit-bot: I haz the power, 2015-02-05 21:13:29]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/901963002/40001

[commit-bot: I haz the power, 2015-02-05 22:14:28]

Committed patchset #1 (id:40001)

[commit-bot: I haz the power, 2015-02-05 22:16:15]

Patchset 1 (id:??) landed as
https://crrev.com/98fccbf697252ed205523a5ff61de0f402b62b8d
Cr-Commit-Position: refs/heads/master@{#314895}