Add a new QUIC ChloExtractor class used by the QuicProxyDispatcher to extract CHLO message from pac…

Add a new QUIC ChloExtractor class used by the QuicProxyDispatcher to extract CHLO message from packets. protected by --quic_use_chlo_extractor

This CL deprecates QuicPacketParser which allocates a clone of the CryptoHandshakeMessage making it somewhat undesirable for use in "cheap" stateless rejects.

Merge internal change: 121416043

R=rch@chromium.org
BUG=

[Ryan Hamilton, 2016-05-13 20:27:09]

https://codereview.chromium.org/1980663003/diff/1/net/quic/quic_flags.h
File net/quic/quic_flags.h (right):

https://codereview.chromium.org/1980663003/diff/1/net/quic/quic_flags.h#newco...
net/quic/quic_flags.h:34: NET_EXPORT_PRIVATE extern bool
FLAGS_quic_use_chlo_extractor;
Sorry, I'm an idiot. I didn't realize where this flag was used when you asked
about it. Yeah, go ahead and nuke this. Sorry!

https://codereview.chromium.org/1980663003/diff/1/net/tools/quic/quic_client.cc
File net/tools/quic/quic_client.cc (right):

https://codereview.chromium.org/1980663003/diff/1/net/tools/quic/quic_client....
net/tools/quic/quic_client.cc:466: const std::string&
QuicClient::latest_response_headers() const {
Can we do using std::string instead?

[Buck, 2016-05-13 21:25:55]

https://codereview.chromium.org/1980663003/diff/1/net/quic/quic_flags.h
File net/quic/quic_flags.h (right):

https://codereview.chromium.org/1980663003/diff/1/net/quic/quic_flags.h#newco...
net/quic/quic_flags.h:34: NET_EXPORT_PRIVATE extern bool
FLAGS_quic_use_chlo_extractor;
On 2016/05/13 20:27:09, Ryan Hamilton wrote:
> Sorry, I'm an idiot. I didn't realize where this flag was used when you asked
> about it. Yeah, go ahead and nuke this. Sorry!

Done.

https://codereview.chromium.org/1980663003/diff/1/net/tools/quic/quic_client.cc
File net/tools/quic/quic_client.cc (right):

https://codereview.chromium.org/1980663003/diff/1/net/tools/quic/quic_client....
net/tools/quic/quic_client.cc:466: const std::string&
QuicClient::latest_response_headers() const {
On 2016/05/13 20:27:09, Ryan Hamilton wrote:
> Can we do using std::string instead?

Done.

[Ryan Hamilton, 2016-05-13 21:42:27]

lgtm