I don’t have the Sources tab (Elements, Resources, Network, Scenarios, Dates, Profiles, Audit, Console).
The Elements tab always reflects the current state of the DOM, so it displays any scripts you enter. EDIT: That seems wrong.
There is a Chrome issue about this: http://code.google.com/p/chromium/issues/detail?id=95352
You can add a specially crafted comment to the entered JavaScript code and it will appear on the Scripts tab (but it still doesn't work on the Elements tab for any reason):
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