0.8dev: Fixed regression in r1522789 which resulted in active mainnav item not being highlighted. Refs #693.

`req.chrome` should be manipulated in `post_process_request` rather than `pre_process_request` since it is assigned a dictionary in `trac.web.chrome:Chrome.prepare_request`.

Patch by Olemis Lang.


git-svn-id: https://svn.apache.org/repos/asf/bloodhound/trunk@1532641 13f79535-47bb-0310-9956-ffa450edef68