Revert of Remove support for Alt-Svc/Alternate Protocol Probability (patchset #7 id:120001 of https://codereview.chromium.org/1699653002/ )

Reason for revert:
This appears to have broken the following bot: https://build.chromium.org/p/chromium.mac/builders/iOS_Device_%28ninja%29/builds/43364

Original issue's description:
> Remove support forAlt-Svc/Alternate Protocol Probability
>
> Committed: https://crrev.com/dced4c771d25317d26a0f6e258c7b7f64d4e8eea
> Cr-Commit-Position: refs/heads/master@{#379652}

TBR=bnc@chromium.org,eroman@chromium.org,mef@chromium.org,rch@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true

Review URL: https://codereview.chromium.org/1773853003

Cr-Commit-Position: refs/heads/master@{#379658}

• chrome/browser/io_thread.cc[diff]
• chrome/browser/io_thread_unittest.cc[diff]
• chrome/browser/resources/net_internals/quic_view.html[diff]
• chrome/common/chrome_switches.cc[diff]
• chrome/common/chrome_switches.h[diff]
• components/cronet/android/cronet_url_request_context_adapter.cc[diff]
• components/cronet/android/url_request_context_adapter.cc[diff]
• ios/chrome/browser/ios_chrome_io_thread.h[diff]
• ios/chrome/browser/ios_chrome_io_thread.mm[diff]
• ios/crnet/CrNet.h[diff]
• ios/crnet/CrNet.mm[diff]
• ios/crnet/crnet_environment.h[diff]
• ios/crnet/crnet_environment.mm[diff]
• net/http/http_network_session.cc[diff]
• net/http/http_network_session.h[diff]
• net/http/http_network_transaction_unittest.cc[diff]
• net/http/http_server_properties.cc[diff]
• net/http/http_server_properties.h[diff]
• net/http/http_server_properties_impl.cc[diff]
• net/http/http_server_properties_impl.h[diff]
• net/http/http_server_properties_impl_unittest.cc[diff]
• net/http/http_server_properties_manager.cc[diff]
• net/http/http_server_properties_manager.h[diff]
• net/http/http_server_properties_manager_unittest.cc[diff]
• net/http/http_stream_factory.cc[diff]
• net/http/http_stream_factory_impl_unittest.cc[diff]
• net/quic/quic_network_transaction_unittest.cc[diff]
• net/quic/quic_stream_factory_test.cc[diff]
• net/spdy/spdy_network_transaction_unittest.cc[diff]