I was testing latest refactor of PerfTools.
When using printOperations() often (but not always) I get 

```
Uncaught TypeError: Cannot read property 'displayName' of undefined
```

in getOperations() on the line:

```
var {displayName, ownerID} = treeSnapshot[instanceID];
```

emitEvent('onBeginReconcilerTimer', debugID, timerType);
  },
  onEndReconcilerTimer(debugID, timerType) {
    emitEvent('onEndReconcilerTimer', debugID, timerType);
  },
  onBeginProcessingChildContext() {
    emitEvent('onBeginProcessingChildContext');
  },
  onEndProcessingChildContext() {
    emitEvent('onEndProcessingChildContext');
  },
  onNativeOperation(debugID, type, payload) {
    emitEvent('onNativeOperation', debugID, type, payload);
  },
  onSetState() {
    emitEvent('onSetState');
  },
  onSetDisplayName(debugID, displayName) {
    emitEvent('onSetDisplayName', debugID, displayName);
  },
  onSetChildren(debugID, childDebugIDs) {
    emitEvent('onSetChildren', debugID, childDebugIDs);
  },
  onSetOwner(debugID, ownerDebugID) {
    emitEvent('onSetOwner', debugID, ownerDebugID);
  },
  onSetText(debugID, text) {
    emitEvent('onSetText', debugID, text);
  },
  onMountRootComponent(debugID) {