Hook createElement for Custom Elements V1

This patch hooks Custom Element V1 creation points and set the Custom
Element State to Undefined when it meets the criteria.

When and how to set the Custom Element State has open issues and is
subject to change. We may need to change when the spec changes.

Most of the logic to create an element[1] is not implemented yet.

[1] https://dom.spec.whatwg.org/#concept-create-element

BUG=594918

Review-Url: https://codereview.chromium.org/2002903002
Cr-Commit-Position: refs/heads/master@{#396078}
5 files changed