ConcurrentHashMap's serialized pseudo fields should be documented.

+ * Serialized pseudo-fields, provided only for jdk7 compatibility.
+ * @serialField segments Segment[]
+ * The segments, each of which is a specialized hash table.
+ * @serialField segmentMask int
+ * Mask value for indexing into segments. The upper bits of a
+ * key's hash code are used to choose the segment.
+ * @serialField segmentShift int
+ * Shift value for indexing within segments.