Bounce tracking should mitigate etag/Last-Modified tracking of http cache resources

[wanderview]

Chrome's initial proposed bounce tracking solution does not trigger on network-level state. This could potentially allow tracking via etag/Last-Modified tracking in the http cache.

The downside of deleting based on network-level state is that some stateless redirectors are high traffic and could suffer performance regressions. For example, vanity sites like gmail.com.

That being said we think this is important and want to find a balanced solution. We have some ideas we plan to pursue after Chrome's initial solution launches.

@Trikolon