add the ability to get token to resources and restore resources from tho...

Some added functionality to workspace. The main motivating factor for this CL was to be able to persist a Resource reference across sessions. This will let us easily restore open files. Other changes

 * added path, isTopLevel properties to Resource
 * added getChild(name), getChildPath(path) to Container

And I'm generally converting `chrome_gen` prefixes to `chrome`.

@keertip