Edit to subdocument causes incorrect tokenization

[njx]

Tested in Mac Chrome 24.0.1312.57

1. Run the gist at https://gist.github.com/njx/4964129 (next to lib folder)
2. In the bottom editor (which is linked to the second rule in the first editor), click at the end of the "background" property line
3. Hit return

Result: In the subeditor, the "background" property turns green, and the token type has changed from "property" to "tag". It's still correct in the main editor.

[marijnh]

This appears to be a different manifestation of #1252 (for which I'm about to push a patch).