Remove support for Alt-Svc/Alternate Protocol Probability

ios/chrome/browser/ios_chrome_io_thread.h

Index: ios/chrome/browser/ios_chrome_io_thread.h
diff --git a/ios/chrome/browser/ios_chrome_io_thread.h b/ios/chrome/browser/ios_chrome_io_thread.h
index f300a7f32e4383b394eac28658a6164ff8ac7ff2..17c7faaca101e43a65364aede385c73f03fc3ad0 100644
--- a/ios/chrome/browser/ios_chrome_io_thread.h
+++ b/ios/chrome/browser/ios_chrome_io_thread.h
@@ -138,7 +138,6 @@ class IOSChromeIOThread : public web::WebThreadDelegate {
     Optional<bool> enable_http2;
     Optional<bool> parse_alternative_services;
     Optional<bool> enable_alternative_service_with_different_host;
-    Optional<double> alternative_service_probability_threshold;
 
     Optional<bool> enable_npn;
 
@@ -350,11 +349,6 @@ class IOSChromeIOThread : public web::WebThreadDelegate {
   static net::QuicTagVector GetQuicConnectionOptions(
       const VariationParameters& quic_trial_params);
 
-  // Returns the alternative service probability threshold specified by
-  // any flags in |quic_trial_params|.
-  static double GetAlternativeProtocolProbabilityThreshold(
-      const VariationParameters& quic_trial_params);
-
   static net::URLRequestContext* ConstructSystemRequestContext(
       Globals* globals,
       net::NetLog* net_log);