Switch to using url bar hiding by default in customtabs

Switch to using url bar hiding by default in customtabs

The extra and customization for this had been added on m45
but the initial default was not hiding the url bar. This
switches the default. Clients can still opt to not hide
the url bar on user scroll.

BUG=527913
Committed: https://crrev.com/43b3af2a120269731f0d7edf44121281b08e3e5a
Cr-Commit-Position: refs/heads/master@{#347509}

[Yusuf, 2015-09-04 17:35:54]

yusufo@chromium.org changed reviewers:
+ tedchoc@chromium.org

[Ted C, 2015-09-04 17:37:00]

lgtm

[Yusuf, 2015-09-04 17:49:54]

The CQ bit was checked by yusufo@chromium.org

[commit-bot: I haz the power, 2015-09-04 17:50:33]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1318003005/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1318003005/1

[commit-bot: I haz the power, 2015-09-04 18:11:34]

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

[commit-bot: I haz the power, 2015-09-04 18:11:35]

Try jobs failed on following builders:
  linux_android_rel_ng on tryserver.chromium.linux (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/linux_android_r...)

[Yusuf, 2015-09-04 21:10:12]

The CQ bit was checked by yusufo@chromium.org

[commit-bot: I haz the power, 2015-09-04 21:10:39]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1318003005/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1318003005/1

[commit-bot: I haz the power, 2015-09-04 22:41:52]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-09-04 22:42:32]

Patchset 1 (id:??) landed as
https://crrev.com/43b3af2a120269731f0d7edf44121281b08e3e5a
Cr-Commit-Position: refs/heads/master@{#347509}