Sent QUIC "PING" frames when a stream is open and the connection

net/quic/quic_protocol.h

Index: net/quic/quic_protocol.h
diff --git a/net/quic/quic_protocol.h b/net/quic/quic_protocol.h
index c586c1d20b9ab328ae62815093cd2ac3a17ce9d1..dd6520918825cd736ce169cf3928cc8ee2ce58cf 100644
--- a/net/quic/quic_protocol.h
+++ b/net/quic/quic_protocol.h
@@ -110,6 +110,9 @@ const int64 kDefaultInitialTimeoutSecs = 120;  // 2 mins.
 const int64 kDefaultTimeoutSecs = 60 * 10;  // 10 minutes.
 const int64 kDefaultMaxTimeForCryptoHandshakeSecs = 5;  // 5 secs.
 
+// Default ping timeout.
+const int64 kPingTimeoutSecs = 15;  // 15 secs.
+
 // We define an unsigned 16-bit floating point value, inspired by IEEE floats
 // (http://en.wikipedia.org/wiki/Half_precision_floating-point_format),
 // with 5-bit exponent (bias 1), 11-bit mantissa (effective 12 with hidden