Gather metrics classifying the cause of the TLS fallback.

net/socket/ssl_client_socket.h

Index: net/socket/ssl_client_socket.h
diff --git a/net/socket/ssl_client_socket.h b/net/socket/ssl_client_socket.h
index cb5e5fbe4c8e15e62eb253f77787e0a3704508f9..d04ad041a086484eca05f866d7dd7da61e1db6ee 100644
--- a/net/socket/ssl_client_socket.h
+++ b/net/socket/ssl_client_socket.h
@@ -13,6 +13,7 @@
 #include "net/base/net_errors.h"
 #include "net/socket/ssl_socket.h"
 #include "net/socket/stream_socket.h"
+#include "net/ssl/ssl_failure_state.h"
 
 namespace net {
 
@@ -129,6 +130,11 @@ class NET_EXPORT SSLClientSocket : public SSLSocket {
   // channel ids are not supported.
   virtual ChannelIDService* GetChannelIDService() const = 0;
 
+  // Returns the state of the handshake when it failed, or |kSSLFailureNone| if
+  // the handshake succeeded. This is used to classify causes of the TLS version
+  // fallback.
+  virtual SSLFailureState GetSSLFailureState() const = 0;
+
  protected:
   void set_negotiation_extension(
       SSLNegotiationExtension negotiation_extension) {