NSMutableSet observerSet = (NSMutableSet)_observersByFilePath.objectForKey(filePath);
if (observerSet == null) {
observerSet = new NSMutableSet();
_observersByFilePath.setObjectForKey(observerSet, filePath);
}
observerSet.addObject(new _ObserverSelectorHolder(observer, selector));
}
/**
* Returns the path that should be used as the cache key for the given file. This
* will return the absolute path of the file (specifically NOT the canonical path)