CustomElements: insert a node

Added test for Step 6.5.2.1
If inclusiveDescendant is custom, then enqueue a custom element
callback reaction with inclusiveDescendant, callback name
"connectedCallback", and an empty argument list.

BUG=594918

Review-Url: https://codereview.chromium.org/2144993002
Cr-Commit-Position: refs/heads/master@{#406520}
1 file changed