Land Recent QUIC Changes.

Land Recent QUIC Changes.

A number of tests define data stream IDs: this CL puts these definitions
in one place in quic_test_utils.h

Merge internal change: 67627075
https://codereview.chromium.org/296853003/

Replace NeuterPacket and RemovePacket with RemoveRetransmittibility,
which removes the retransmittibility property from a packet and it's
associated transmissions.

Merge internal change: 67615222
https://codereview.chromium.org/286933010/

Cleanup changes to fix the using:: order.

Merge internal change: 67541632,, 67612445
https://codereview.chromium.org/297773002/

Remove QuicSentPacketManager's DiscardUnackedPacket method now that it's
not necessary.

Merge internal change: 67542370
https://codereview.chromium.org/290333005/

Garbage collect QUIC entropy map as gaps are filled.  Not flag protected.

Merge internal change: 67521743
https://codereview.chromium.org/296053006/

Extract entropy tracking from QuicReceivedPacketManager into its own
class in preparation for garbage collecting unneeded entropy history.

Extract QUIC entropy tracking into a separate class, no behavior change.

Merge internal change: 67273904
https://codereview.chromium.org/294143004/

Remove check for an impossible condition.  StopWaiting frames with
least_unacked > packet sequence number are illegal.  Largest observed is
guaranteed to be >= the StopWaiting packet sequence number.

Remove impossible condition from an if.

Merge internal change: 67268376
https://codereview.chromium.org/292983009/

R=rch@chromium.org

Review URL: https://codereview.chromium.org/297513005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@272158 0039d316-1c4b-4281-b951-d872f2087c98