Close idle H2 sockets when SpdySession is initialized.

net/http/http_network_transaction_unittest.cc

Index: net/http/http_network_transaction_unittest.cc
diff --git a/net/http/http_network_transaction_unittest.cc b/net/http/http_network_transaction_unittest.cc
index ccd153601a1935c9570eee1a0abcd9c76e69d7af..dc8225223284764d240f90ce8094bfee4a3c9ab8 100644
--- a/net/http/http_network_transaction_unittest.cc
+++ b/net/http/http_network_transaction_unittest.cc
@@ -684,6 +684,7 @@ class CaptureGroupNameSocketPool : public ParentPool {
                      std::unique_ptr<StreamSocket> socket,
                      int id) override {}
   void CloseIdleSockets() override {}
+  void CloseIdleSocketsInGroup(const std::string& group_name) override {}
   int IdleSocketCount() const override { return 0; }
   int IdleSocketCountInGroup(const std::string& group_name) const override {
     return 0;