Fix waiting count stat in aggregate manager.
Fix waiting count stat in aggregate manager.

Only count mDirtyAggregateObjects.size() when computing the number of
waiting aggregates since the objects in the mObjectsByPriority lists
that were also being counted should still be in mDirtyAggregateObjects.

sirikata/sirikata,sirikata/sirikata,sirikata/sirikata,sirikata/sirikata,sirikata/sirikata,sirikata/sirikata,sirikata/sirikata,sirikata/sirikata