chromium relnote: Making QuicTestClient reads mockable.

chromium relnote: Making QuicTestClient reads mockable.

Internal relnote: Droping expired TTL correctly for outbound packets.

When we switched to doing proper backend picking for UDP proxy sessions,
we also stopped using ProcessPacket for outbound packets, but still left
all the handling code in place, obfuscating the new code path.

This CL removes the lingering code, applies TTL correctly on the
outbound path. This also removes reaping connections during the outbound
path or during write failures, but that simply means we only apply
connection timeouts when getting new incoming traffic which seems
sufficient.

Not flag protected because it's a big messy change.

Merge internal change: 130124951

R=rch@chromium.org

[Ryan Hamilton, 2016-08-15 23:25:19]

lgtm