DnsTransaction::RecordLostPacketsIfAny shouldn't crash if some attempts failed to connect and thus …

net/dns/dns_transaction_unittest.cc

Index: net/dns/dns_transaction_unittest.cc
diff --git a/net/dns/dns_transaction_unittest.cc b/net/dns/dns_transaction_unittest.cc
index f6fb8e5d795e97366097615a7ff281d8980a1d5a..262e06cde07476321ed0e42505b15bed921c46be 100644
--- a/net/dns/dns_transaction_unittest.cc
+++ b/net/dns/dns_transaction_unittest.cc
@@ -185,8 +185,10 @@ class TestSocketFactory : public MockClientSocketFactory {
       const RandIntCallback& rand_int_cb,
       net::NetLog* net_log,
       const net::NetLog::Source& source) OVERRIDE {
-    if (create_failing_sockets_)
+    if (create_failing_sockets_) {

[szym, 2013/05/29 17:09:42]

Suggest renaming this field to |fail_next_socket_| since after creating one
socket the behavior reverts to normal.

[mef, 2013/05/29 17:24:04]

Done.

+      create_failing_sockets_ = false;
       return new FailingUDPClientSocket(&empty_data_, net_log);
+    }
     SocketDataProvider* data_provider = mock_data().GetNext();
     TestUDPClientSocket* socket = new TestUDPClientSocket(this,
                                                           data_provider,
@@ -865,6 +867,21 @@ TEST_F(DnsTransactionTest, ConnectFailure) {
   EXPECT_TRUE(helper0.Run(transaction_factory_.get()));
 }
 
+TEST_F(DnsTransactionTest, ConnectFailureDoesntCrashInRecordLostPacketsIfAny) {

[szym, 2013/05/29 17:09:42]

suggest just calling the test "ConnectFailureFollowedBySuccess"

[mef, 2013/05/29 17:24:04]

Done.

+  // Fallback on server failure.

[szym, 2013/05/29 17:09:42]

suggest: "// Retry after failure."

[mef, 2013/05/29 17:24:04]

Done.

+  config_.attempts = 2;
+  ConfigureFactory();
+  // First server connection attempt fails.
+  transaction_ids_.push_back(0);  // Needed to make a DnsUDPAttempt.
+  socket_factory_->create_failing_sockets_ = true;
+  // Second DNS query succeeds.
+  AddAsyncQueryAndResponse(0 /* id */, kT0HostName, kT0Qtype,
+                           kT0ResponseDatagram, arraysize(kT0ResponseDatagram));
+  TransactionHelper helper0(kT0HostName, kT0Qtype, kT0RecordCount);
+  // Expect no crash here!

[szym, 2013/05/29 17:09:42]

unnecessary comment

[mef, 2013/05/29 17:24:04]

Done.

+  EXPECT_TRUE(helper0.Run(transaction_factory_.get()));
+}
+
 TEST_F(DnsTransactionTest, TCPLookup) {
   AddAsyncQueryAndRcode(kT0HostName, kT0Qtype,
                         dns_protocol::kRcodeNOERROR | dns_protocol::kFlagTC);