Changes based on code review and added listener to GridManager and unit test.
Change-Id: Ida593a7e3cc7d4fd9bd6f44a4455145114484650
Former-commit-id: 1e492b81ff [formerly 1cd076671c [formerly 7f70c2f65453db6bf3097ae8157511c38a36b136]]
Former-commit-id: 1cd076671c
Former-commit-id: 972db12324