* Don't show "context" for classes without either contextType or contextTypes
* For classes with contextTypes, change the label to "legacy context" instead

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Originally reported by @gaearon via https://github.com/bvaughn/react-devtools-experimental/issues/368
case ElementTypeClass:
        if (idToContextsMap !== null) {
          const id = getFiberID(getPrimaryFiber(fiber));
          const prevContexts = idToContextsMap.has(id)