Landing Recent QUIC changes until 6:40 PM, Mar 5, 2019 UTC-5

Refactor QuicFramer connection ID read code

This CL refactors how we read connection IDs to allow future changes
that will use different default lengths based on what is configured for
this connection.

Merge internal change: 236935043

https://chromium-review.googlesource.com/c/1504509/

Make a test involving connection IDs more future-proof

Merge internal change: 236924820

https://chromium-review.googlesource.com/c/1504508/

Remove some fixed packet lengths.

This CL moves us yet another step closer to being connection ID length
agnostic in the lower layers such as the QuicFramer. More specifically,
it replaces instances of PACKET_8BYTE_CONNECTION_ID with
connection_id.length(). This is safe to use without flag protection
because we have code in all connection ID entry points to ensure that
their length is 8.

Merge internal change: 236894613

https://chromium-review.googlesource.com/c/1504506/

R=rch@chromium.org

Change-Id: I488160120ad125ff342e5983cba22946dc437183
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1504510
Commit-Queue: Victor Vasiliev <vasilvv@chromium.org>
Commit-Queue: Ryan Hamilton <rch@chromium.org>
Reviewed-by: Ryan Hamilton <rch@chromium.org>
Cr-Commit-Position: refs/heads/master@{#637998}
11 files changed