Landing Recent QUIC Changes.

Add pending_timer_transmission_count_ to QuicSentPacketManager, to
ensure that crypto and TLP packets are retransmitted even if congestion
blocked.

Seems to completely fix rare flake in b/16979022
(EndToEndTest.LargePostZeroRTTFailure\*).

Prior to this CL would fail ~6 times (out of 3000), now 0 failures.

Enabled EndToEndTest::LargePostZeroRTTFailure unittest.

Merge internal change: 73541149
https://codereview.chromium.org/487423002/


Remove FLAGS_enable_quic_pacing.

Merge internal change: 73538379
https://codereview.chromium.org/490673003/


Delete unimplemented constructor.

Merge internal change: 73532475
https://codereview.chromium.org/480563007/


Add the "Ms" suffix to the "kMaxDelayedAckTime" constant name to suggest
the time unit.

Merge internal change: 73424693
https://codereview.chromium.org/470803005/


net/tools/quic/quic_dispatcher.h use forward declarations instead of
including net/tools/quic/quic_dispatcher.h.

Merging of forward declarations CL. Deleted unused forward declaration.

Merge internal change: 73326621
https://codereview.chromium.org/472823004/

R=rch@chromium.org

Review URL: https://codereview.chromium.org/492803002

git-svn-id: http://src.chromium.org/svn/trunk/src/net@290897 4ff67af0-8c30-449e-8e8b-ad334ec8d88c
Also declare the transport_security_state_ member as const.

R=rch@chromium.org
BUG=399457

Review URL: https://codereview.chromium.org/456953002

git-svn-id: http://src.chromium.org/svn/trunk/src/net@290969 4ff67af0-8c30-449e-8e8b-ad334ec8d88c