Revert of Remove support for Alt-Svc/Alternate Protocol Probability

ios/crnet/crnet_environment.h

Index: ios/crnet/crnet_environment.h
diff --git a/ios/crnet/crnet_environment.h b/ios/crnet/crnet_environment.h
index ec86cd3391c883e797151f3f0dbe7e42767a36e2..6091ee05bef01e78b4139de8773759899d52ccfb 100644
--- a/ios/crnet/crnet_environment.h
+++ b/ios/crnet/crnet_environment.h
@@ -92,10 +92,16 @@
   void set_sdch_pref_store_filename(const std::string& pref_store) {
     sdch_pref_store_filename_ = pref_store;
   }
+  void set_alternate_protocol_threshold(double threshold) {
+    alternate_protocol_threshold_ = threshold;
+  }
 
   bool spdy_enabled() const { return spdy_enabled_; }
   bool quic_enabled() const { return quic_enabled_; }
   bool sdch_enabled() const { return sdch_enabled_; }
+  double alternate_protocol_threshold() const {
+    return alternate_protocol_threshold_;
+  }
 
   // Clears the network stack's disk cache.
   void ClearCache(ClearCacheCallback callback);
@@ -135,6 +141,7 @@
   bool quic_enabled_;
   bool sdch_enabled_;
   std::string sdch_pref_store_filename_;
+  double alternate_protocol_threshold_;
 
   static CrNetEnvironment* chrome_net_;
   scoped_ptr<base::Thread> network_io_thread_;