Measure speedreader performance impact

[iefremov]

We need to answer the following:

We need this answers for speedreader as a standalone library and as a browser component.

1. How much memory does speedreader consume
2. How much time does the speedreader transformation take
3. How much time does the speedreader analyze phase take

We also need a list of metrics to watch locally and metrics that potentially will be collected via P3A

[mattmcalister]

These questions need to be written with answer buckets