Implement Node.ownerScope

Implement Node.ownerScope

The ownerScope property is equivalent to walking up the parentNode
pointers until you hit the top and returning that node if it's a
Document or ShadowRoot.

This means that the ownerScope of ShadowRoot and Document is always
itself, and the ownerScope of an Element that is not the descendant
of a ShadowRoot, and is not in the document is null.

R=eseidel@chromium.org

Committed: https://chromium.googlesource.com/external/mojo/+/41f3a39e061bf94475f9393df420c675f679234c

[eseidel, 2014-12-17 23:58:37]

eseidel@chromium.org changed reviewers:
+ eseidel@chromium.org

[eseidel, 2014-12-17 23:58:37]

The CQ bit was checked by eseidel@chromium.org

[eseidel, 2014-12-17 23:58:37]

lgtm

[esprehn, 2014-12-17 23:58:55]

esprehn@chromium.org changed reviewers:
- eseidel@chromium.org

[esprehn, 2014-12-17 23:59:37]

esprehn@chromium.org changed reviewers:
+ eseidel@chromium.org

[commit-bot: I haz the power, 2014-12-18 00:00:08]

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

[commit-bot: I haz the power, 2014-12-18 00:00:09]

Commit queue rejected this change because it did not recognize the base URL.
Please commit your change manually.

[esprehn, 2014-12-18 00:05:19]

Committed patchset #2 (id:20001) manually as
41f3a39e061bf94475f9393df420c675f679234c (presubmit successful).