Add a probability to Alternate-Protocol support.

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 167c46307c1d169188e88f47c7c34f88fbf51d4d..c43955820841858110c2ca9cecdf9ddd5406e78b 100644
--- a/chrome/common/chrome_switches.cc
+++ b/chrome/common/chrome_switches.cc
@@ -52,6 +52,12 @@ const char kAllowOutdatedPlugins[]          = "allow-outdated-plugins";
 // URLs. This provides an override to get the old insecure behavior.
 const char kAllowRunningInsecureContent[]   = "allow-running-insecure-content";
 
+// Specifies the threshold to be used when determining of an Alternate-Protocol
+// advertisement will be honored. If the advertised probability is larger
+// than the threshold, then it will be honored.
+const char kAlternateProtocolProbabilityThreshold[] =
+    "alternate-protocol-probability-threshold";
+
 // Prevents Chrome from requiring authorization to run certain widely installed
 // but less commonly used plug-ins.
 const char kAlwaysAuthorizePlugins[]        = "always-authorize-plugins";