Land Recent QUIC Changes.

Land Recent QUIC Changes.

Removed QUIC_VERSION_19 from kSupportedQuicVersions. Will
submit a separate CL after making sure all tests pass with
QUIC_VERSION_19.

Introduces QUIC_VERSION_19, connection level flow control.
QuicConnection now has its own flow_controller_ which aggregates bytes
sent/received/consumed from all the streams on a given connection.

WINDOW_UPDATE and BLOCKED frames are sent with a stream_id of 0 when
they refer to the connection.

On receipt of a WINDOW_UPDATE which unblocks the connection level flow
control, all blocked streams are given a chance to write through a call
to OnCanWrite.

QUIC_VERSION_19: connection flow control. Protected behind
--FLAGS_enable_quic_connection_flow_control

Merge internal change: 66020935
https://codereview.chromium.org/265953003/

New QUIC SendAlgorithmInterface which replaces OnPacketAcked,
OnPacketLost, OnPacketAbandoned, and OnRttUpdated with a single
OnCongestionEvent method.

Merge internal change: 66018835
https://codereview.chromium.org/264743011/

Move TransmissionInfo from QuicUnackedPacketMap to QuicProtocol and add
a simple bytes_in_flight accessor.

Merge internal change: 65886839
https://codereview.chromium.org/265993003/

If stream N is added to the write blocked list, and later a
WINDOW_UPDATE frame arrives for the same stream, then stream N will
added for a second time to the write blocked list.

This is wrong - a stream should only be on the write blocked list once.
The write blocked list is implemented as a deque. This CL adds a
parallel set<QuicStreamId> which also keeps track of blocked streams,
but allows more efficient membership testing. This is used to ensure no
duplicate stream IDs end up in the write blocked list.

Don't allow duplicate IDs in QUIC write blocked list.

Merge internal change: 65878293
https://codereview.chromium.org/261983003/

Sync'ing changes with internal source tree. Minor formatting changes.

Merge internal change: 65851919
https://codereview.chromium.org/265813010/

Test-only change to clean up QuicSentPacketManagerTest in order to make
changing the SendAlgorithmInterface easier.

Merge internal change: 65816291
https://codereview.chromium.org/268623010/

R=rch@chromium.org

Review URL: https://codereview.chromium.org/265833015

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@268980 0039d316-1c4b-4281-b951-d872f2087c98