I haven't reviewed the rest of the code, but should this method be called `getFeatureInfoRequestParams()`.  It would be implemented by the superclass, as well as this class, which adds these couple of extra parameters in there.

Also, based on the above (where start/end times are not properties of this object, and the values are instead passed in from the caller), the signature would have to be something like:

```javascript
getFeatureInfoRequestParams(temporalExtent)
```