[nacltoons] Reference resources directly from checkout location

This allows editing of files in-place to take effect
without re-publishing.

Review URL: https://codereview.chromium.org/12413017

git-svn-id: https://nativeclient-sdk.googlecode.com/svn/trunk/src@1532 050acbb0-2703-11df-ab0a-9f3f633ae91d