reading https://github.com/mozilla-b2g/gaia/blob/master/tests/performance/performance_helper.js#L86-L91, I think we miss something.

In https://github.com/mozilla-b2g/gaia/blob/master/tests/performance/performance_helper.js#L86-L91, we should do this instead:
```javascript
      sendResults('mozPerfDuration', { title: title, values: values });
```

and here:

```javascript
mozPerfDurations[content.title] = content.values;
```