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

chrome/common/chrome_switches.cc

Index: chrome/common/chrome_switches.cc
diff --git a/chrome/common/chrome_switches.cc b/chrome/common/chrome_switches.cc
index d32a32f3ae75c94afb81afdc78a84d52741e1935..b1be5b9616a1f3d976ac6b18292581f5f5dca6e8 100644
--- a/chrome/common/chrome_switches.cc
+++ b/chrome/common/chrome_switches.cc
@@ -65,6 +65,12 @@
 // By default, an https page cannot run JavaScript, CSS or plugins from http
 // URLs. This provides an override to get the old insecure behavior.
 const char kAllowRunningInsecureContent[]   = "allow-running-insecure-content";
+
+// Specifies the probability threshold for alternative services: an advertised
+// alternative service will only be honored if the advertised probability is
+// greater than or equal to this threshold.
+const char kAlternativeServiceProbabilityThreshold[] =
+    "alternative-service-probability-threshold";
 
 // Prevents Chrome from requiring authorization to run certain widely installed
 // but less commonly used plugins.