net: disable SSLv3 fallback.

net/ssl/ssl_config.h

Index: net/ssl/ssl_config.h
diff --git a/net/ssl/ssl_config.h b/net/ssl/ssl_config.h
index 27312147f0f5beff209c1afc2044e2d12d1fbe74..1deaf6e653bfd7bf8497b0ab5eeac3fff7a96dc0 100644
--- a/net/ssl/ssl_config.h
+++ b/net/ssl/ssl_config.h
@@ -32,6 +32,9 @@ NET_EXPORT extern const uint16 kDefaultSSLVersionMin;
 // Default maximum protocol version.
 NET_EXPORT extern const uint16 kDefaultSSLVersionMax;
 
+// Default minimum protocol version that it's acceptable to fallback to.
+NET_EXPORT extern const uint16 kDefaultSSLVersionFallbackMin;
+
 // A collection of SSL-related configuration settings.
 struct NET_EXPORT SSLConfig {
   // Default to revocation checking.
@@ -73,6 +76,12 @@ struct NET_EXPORT SSLConfig {
   uint16 version_min;
   uint16 version_max;
 
+  // version_fallback_min contains the minimum version that is acceptable to
+  // fallback to. Versions before this may be tried to see whether they would
+  // have succeeded and thus to give a better message to the user, but the
+  // resulting connection won't be used in these cases.
+  uint16 version_fallback_min;
+
   // Presorted list of cipher suites which should be explicitly prevented from
   // being used in addition to those disabled by the net built-in policy.
   //