Make sure to lazyReattach a distributed node if it is already attached

For Shadow DOM v0, InsertionPoint::setDistributedNodes() is calling
lazyReattachIfAttached for distributed nodes, if necessary.

The same thing should be done for Shadow DOM v1 too. Unless that, the old layout
object will be re-used wrongly.

BUG=531990,622185

Review-Url: https://codereview.chromium.org/2086013003
Cr-Commit-Position: refs/heads/master@{#401512}
5 files changed