Add histogram to track NPN/ALPN.

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 0e32ed6d39e27cd60e6f928d4a03a7857113c786..8eea20cd0ded6f75b2c56acc14bf2728a8a91a5c 100644
--- a/net/socket/ssl_client_socket.h
+++ b/net/socket/ssl_client_socket.h
@@ -79,6 +79,20 @@ class NET_EXPORT SSLClientSocket : public SSLSocket {
                                 // the first protocol in our list.
   };
 
+  // TLS extension used to negotiate protocol.  Recorded in UMA, do not change
+  // or reuse values.
+  enum SSLProtocolNegotiation {
+    // Unknown.
+    PN_UNKNOWN = -1,
+    // Application-Layer Protocol Negotiation.
+    PN_ALPN = 0,
+    // Next Protocol Negotiation used.
+    PN_NPN = 500,
+    // Next Protocol Negotiation used, but there was no overlap between client
+    // and server supported protocols.  Fallback to first one on client's list.
+    PN_NPN_NO_OVERLAP = 1000,

[davidben, 2014/09/19 21:09:17]

It seems strange to have this enum with large numbers and also have a value
(PN_NPN_NO_OVERLAP) that's not set externally. How about just

enum SSLProtocolNegotiation {
  kProtocolNone = 0,
  kProtocolALPN = 1,
  kProtocolNPN = 2,
};

(Our style seems slightly confused as to whether we do kConstantsLikeThis or
CONSTANTS_LIKE_THAT, but this is consistent with the other one in this class.)

And then munge into a single number internally if you want a single histogram.

[Bence, 2014/10/03 10:50:22]

Done.

I changed to kExtension* to better distinguish TLS extensions (NPN, ALPN) from
protocols they negotiate (HTTP/1, SPDY, QUIC).

+  };
+
   // StreamSocket:
   virtual bool WasNpnNegotiated() const OVERRIDE;
   virtual NextProto GetNegotiatedProtocol() const OVERRIDE;
@@ -150,6 +164,9 @@ class NET_EXPORT SSLClientSocket : public SSLSocket {
 
   virtual void set_protocol_negotiated(NextProto protocol_negotiated);
 
+  void set_protocol_negotiation(
+      enum SSLProtocolNegotiation protocol_negotiation);

[davidben, 2014/09/19 21:09:17]

No 'enum' prefix in C++.

[Bence, 2014/10/03 10:50:22]

Done.

+
   // Returns the ChannelIDService used by this socket, or NULL if
   // channel ids are not supported.
   virtual ChannelIDService* GetChannelIDService() const = 0;
@@ -162,6 +179,10 @@ class NET_EXPORT SSLClientSocket : public SSLSocket {
   // Public for ssl_client_socket_openssl_unittest.cc.
   virtual bool WasChannelIDSent() const;
 
+  // Record which TLS extension was used to negotiate protocol and protocol
+  // chosen in a UMA histogram.
+  void RecordProtocolNegotiation();
+
  protected:
   virtual void set_channel_id_sent(bool channel_id_sent);
 
@@ -219,6 +240,8 @@ class NET_EXPORT SSLClientSocket : public SSLSocket {
   bool signed_cert_timestamps_received_;
   // True if a stapled OCSP response was received.
   bool stapled_ocsp_response_received_;
+  // Protocol negotiation extension used.
+  enum SSLProtocolNegotiation protocol_negotiation_;
 };
 
 }  // namespace net