Provides a debug DebugWindow that is bound to the goog.debug.Logger.
It handles log messages and writes them to the DebugWindow. This doesn't
provide a lot of functionality that the old Gmail logging infrastructure
provided like saving debug logs for exporting to the server. Now that we
have an event-based logging infrastructure, we can encapsulate that
functionality in a separate class.
Creates a valid cookie key name which is scoped to the given identifier.
Substitutes all occurences of invalid cookie name characters (whitespace,
';', and '=') with '_', which is a valid and readable alternative.