Merge "Don't allow invalid Uris to be added as observers."

            // Look to see if the proper child already exists

            String segment = getUriSegment(uri, index);

            if (segment == null) {

                throw new IllegalArgumentException("Invalid Uri (" + uri + ") used for observer");

            }

            int N = mChildren.size();

            for (int i = 0; i < N; i++) {

                ObserverNode node = mChildren.get(i);