Add a probability to Alternate-Protocol support.

chrome/browser/io_thread.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CHROME_BROWSER_IO_THREAD_H_
 #define CHROME_BROWSER_IO_THREAD_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 154 matching lines @@
     Optional<bool> force_spdy_single_domain;
     Optional<bool> enable_spdy_compression;
     Optional<bool> enable_spdy_ping_based_connection_checking;
     Optional<net::NextProto> spdy_default_protocol;
     net::NextProtoVector next_protos;
     Optional<string> trusted_spdy_proxy;
     Optional<bool> force_spdy_over_ssl;
     Optional<bool> force_spdy_always;
     std::set<net::HostPortPair> forced_spdy_exclusions;
     Optional<bool> use_alternate_protocols;
+    Optional<double> alternate_protocol_probability_threshold;
     Optional<bool> enable_websocket_over_spdy;
 
     Optional<bool> enable_quic;
     Optional<bool> enable_quic_pacing;
     Optional<bool> enable_quic_time_based_loss_detection;
     Optional<bool> enable_quic_port_selection;
     Optional<size_t> quic_max_packet_length;
     net::QuicTagVector quic_connection_options;
     Optional<std::string> quic_user_agent_id;
     Optional<net::QuicVersionVector> quic_supported_versions;
@@ skipping 166 matching lines @@
   // |command_line| or |quic_trial_params|.
   static net::QuicTagVector GetQuicConnectionOptions(
       const base::CommandLine& command_line,
       const VariationParameters& quic_trial_params);
 
   // Returns the list of QUIC tags represented by the comma separated
   // string in |connection_options|.
   static net::QuicTagVector ParseQuicConnectionOptions(
       const std::string& connection_options);
 
+  // Returns the alternate protocol probability threshold specified by
+  // any flags in |command_line| or |quic_trial_params|.
+  static double GetAlternateProtocolProbabilityThreshold(
+      const base::CommandLine& command_line,
+      const VariationParameters& quic_trial_params);
+
   // The NetLog is owned by the browser process, to allow logging from other
   // threads during shutdown, but is used most frequently on the IOThread.
   ChromeNetLog* net_log_;
 
   // The extensions::EventRouterForwarder allows for sending events to
   // extensions from the IOThread.
   extensions::EventRouterForwarder* extension_event_router_forwarder_;
 
   // These member variables are basically global, but their lifetimes are tied
   // to the IOThread.  IOThread owns them all, despite not using scoped_ptr.
@@ skipping 40 matching lines @@
   bool is_spdy_disabled_by_policy_;
 
   base::WeakPtrFactory<IOThread> weak_factory_;
 
   const base::TimeTicks creation_time_;
 
   DISALLOW_COPY_AND_ASSIGN(IOThread);
 };
 
 #endif  // CHROME_BROWSER_IO_THREAD_H_