Bug 866232 - Add an APZCTreeManager to encapsulate the multiple APZCs corresponding to a given layer tree. r=
Bug 866232 - Add code to build the APZC tree on layer updates. r=
Bug 866232 - Some documentation/variable renaming cleanup. r=
Bug 866232 - Extract a GetCurrentAsyncTransform method in APZC. r=
Bug 866232 - Add visible region tracking and hit-testing code for APZCTreeManager. r=