DataReductionProxyMetricsObserver tracks various UMA on page size as requests and bytes.

It would be interesting to seperate the percents and some of the other metrics into LessThan10Requests and AtLeast10Requests at some point.

In general, this could apply to a new class of metrics (Clients.DataReductionProxy.AtLeast10NetworkRequests.*) for the metrics that we are interested in.