Project: mesos
Issue MESOS-2735: Change the interaction between the slave and the resource estimator from polling to pushing 
This will make the semantics more clear. The resource estimator can control the speed of sending resources estimation to the slave. To avoid cyclic dependency, slave will register a callback with the resource estimator and the resource estimator will simply invoke that callback when there's a new estimation ready. The callback will be a defer to the slave's main event queue.
Story points: 3