@Override
    public boolean equals(Object obj) {
        return (obj == this) ||
               (obj instanceof StateMetricContext && ((StateMetricContext)obj).data.equals(data));
    }
A context implementation whose identity is the key and values such that this can be used as
a key in metrics lookups.

@author Simon Thoresen Hult
container-core/src/main/java/com/yahoo/container/jdisc/state/StateMetricContext.java