[net/dns] Fix how DnsTransaction computes next server index after fallback.

net/dns/dns_transaction_unittest.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "net/dns/dns_transaction.h"
 
 #include "base/bind.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/scoped_vector.h"
 #include "base/rand_util.h"
@@ skipping 627 matching lines @@
   ConfigureFactory();
 
   // Responses for first request.
   AddQueryAndTimeout(kT0HostName, kT0Qtype);
   AddAsyncQueryAndRcode(kT0HostName, kT0Qtype, dns_protocol::kRcodeSERVFAIL);
   AddQueryAndTimeout(kT0HostName, kT0Qtype);
   AddAsyncQueryAndRcode(kT0HostName, kT0Qtype, dns_protocol::kRcodeSERVFAIL);
   AddAsyncQueryAndRcode(kT0HostName, kT0Qtype, dns_protocol::kRcodeNXDOMAIN);
   // Responses for second request.
   AddAsyncQueryAndRcode(kT1HostName, kT1Qtype, dns_protocol::kRcodeSERVFAIL);
+  AddAsyncQueryAndRcode(kT1HostName, kT1Qtype, dns_protocol::kRcodeSERVFAIL);
   AddAsyncQueryAndRcode(kT1HostName, kT1Qtype, dns_protocol::kRcodeNXDOMAIN);
 
   TransactionHelper helper0(kT0HostName, kT0Qtype, ERR_NAME_NOT_RESOLVED);
   TransactionHelper helper1(kT1HostName, kT1Qtype, ERR_NAME_NOT_RESOLVED);
 
   EXPECT_TRUE(helper0.RunUntilDone(transaction_factory_.get()));
   EXPECT_TRUE(helper1.Run(transaction_factory_.get()));
 
   unsigned kOrder[] = {
       0, 1, 2, 0, 1,    // The first transaction.
-      1, 2,             // The second transaction starts from the next server.
+      1, 2, 0,          // The second transaction starts from the next server.
   };
   CheckServerOrder(kOrder, arraysize(kOrder));
 }
 
 TEST_F(DnsTransactionTest, SuffixSearchAboveNdots) {
   config_.ndots = 2;
   config_.search.push_back("a");
   config_.search.push_back("b");
   config_.search.push_back("c");
   config_.rotate = true;
@@ skipping 242 matching lines @@
   AddSocketData(make_scoped_ptr(
       new DnsSocketData(1 /* id */, kT0HostName, kT0Qtype, ASYNC, true)));
 
   TransactionHelper helper0(kT0HostName, kT0Qtype, ERR_DNS_TIMED_OUT);
   EXPECT_TRUE(helper0.RunUntilDone(transaction_factory_.get()));
 }
 
 }  // namespace
 
 }  // namespace net