I created a few docs for the Timeline. These docs explain the basic design of Timeline and how to extend Timeline by creating a producer. In my previous post, I explained the features of the Timeline User Interface. This marks the completion of GSoC with all the code and docs complete.
Design Overview : https://wiki.mozilla.org/DevTools/Graphical_Timeline_v1
Creating a producer: https://wiki.mozilla.org/DevTools/Timeline/Creating_and_registering_producer
Complete feature list : http://grssam.com/2012/08/gsoc-comes-to-an-end/