Add a new kMIDS (Max Incoming Dynamic Streams) config option, to eventually replace kMSPC.

net/quic/quic_config_test.cc

Index: net/quic/quic_config_test.cc
diff --git a/net/quic/quic_config_test.cc b/net/quic/quic_config_test.cc
index c347b970eceb402873ce2177f168a305c0c5be1e..7d813a55ad77cfaa18f4ab5008a811d53217f24e 100644
--- a/net/quic/quic_config_test.cc
+++ b/net/quic/quic_config_test.cc
@@ -181,9 +181,8 @@ TEST_F(QuicConfigTest, MissingOptionalValuesInSHLO) {
 }
 
 TEST_F(QuicConfigTest, MissingValueInCHLO) {
+  // Server receives CHLO with missing kICSL.
   CryptoHandshakeMessage msg;
-  msg.SetValue(kICSL, 1);
-  // Missing kMSPC. KATO is optional.
   string error_details;
   const QuicErrorCode error =
       config_.ProcessPeerHello(msg, CLIENT, &error_details);
@@ -191,9 +190,8 @@ TEST_F(QuicConfigTest, MissingValueInCHLO) {
 }
 
 TEST_F(QuicConfigTest, MissingValueInSHLO) {
+  // Client receives SHLO with missing kICSL.
   CryptoHandshakeMessage msg;
-  msg.SetValue(kMSPC, 3);
-  // Missing ICSL. KATO is optional.
   string error_details;
   const QuicErrorCode error =
       config_.ProcessPeerHello(msg, SERVER, &error_details);