When innerWindow is restored from the history state, we do not receive
content-document-global-created notification, but would still like to know
that window is now using a different inner window to reset the state.
This introduces a new notification juggler-dom-window-reused.
At the same time, goBack()/goForward() sometimes do not initiate
navigation synchronously, so our check for pendingNaivgationId() does
not work. Instead, we rely on canGoBack, and assume that client will
not need the navigationId synchronously.
