CustomElements: adoptedCallback should be invoked in tree order

3.3 For each inclusiveDescendant in node’s shadow-including inclusive
    descendants, in shadow-including tree order, run the adopting steps
    with inclusiveDescendant and oldDocument.

BUG=594918

Review-Url: https://codereview.chromium.org/2247663002
Cr-Commit-Position: refs/heads/master@{#412167}
1 file changed