Add hangout ID in addition to URL

In an effort to debug the "wild hangout URL appears" double-set
in-the-wrong-hangout errors, store the hangout ID when setting the
hangout URL.  This is just for logging presently; the ID is not used for
any other logic.
Don't trigger saves on deleted sessions.
Merge branch 'master' into hangoutid

Conflicts:
	test/test.mock-hangout.selenium.js
Merge branch 'master' into nocdn
Merge branch 'hangoutid' into nocdn
Fix race for .cancel-autohide test