This patch returns each resource's extraData model attribute to be a

plain JavaScript object. The new extra data API (via RB.ExtraData) is

exposed through model.extraData instead of

model.attributes.extraData. This will prevent extensions that use the

old API from breaking but still expose the new API. JS tests have been

updated to reflect these changes.

Ran JS tests.

Tested with the rbstopwatch extension. It worked with this patch

applied.