Firebug cd equivalent in Chrome console / developer tools

In firebug, you can use the cd command to change the console context to an iframe. I need this when develo开发者_开发百科ping a facebook app to debug my javascript inside the iframe.

How do you do this in google chrome?

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No "cd" command yet, but it seems that we'll have a "dropdown list with all iframes to allow selecting current evaluation context for console expressions" in upcoming releases.
See http://trac.webkit.org/changeset/91839