Change HostResolverImplDnsTest.NoIPv6OnWifi to no longer leak

net/dns/host_resolver_impl_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/host_resolver_impl.h"
 
 #include <algorithm>
 #include <memory>
 #include <string>
 #include <tuple>
@@ skipping 2389 matching lines @@
   proc_->SignalMultiple(3u);
 
   EXPECT_THAT(requests_[0]->WaitForResult(), IsOk());
   EXPECT_TRUE(requests_[0]->HasOneAddress("192.168.0.1", 80));
   EXPECT_THAT(requests_[1]->WaitForResult(), IsOk());
   EXPECT_TRUE(requests_[1]->HasOneAddress("192.168.0.2", 80));
   EXPECT_THAT(requests_[2]->WaitForResult(), IsOk());
   EXPECT_TRUE(requests_[2]->HasOneAddress("192.168.0.3", 80));
 }
 
-// TODO(crbug.com/728808): This test causes HttpNetworkTransactionTests to crash
-// on iOS.
-#if defined(OS_IOS)
-#define MAYBE_NoIPv6OnWifi DISABLED_NoIPv6OnWifi
-#else
-#define MAYBE_NoIPv6OnWifi NoIPv6OnWifi
-#endif
-TEST_F(HostResolverImplDnsTest, MAYBE_NoIPv6OnWifi) {
+TEST_F(HostResolverImplDnsTest, NoIPv6OnWifi) {
+  // CreateSerialResolver will destroy the current resolver_ which will attempt
+  // to remove itself from the NetworkChangeNotifier. If this happens after a
+  // new NetworkChangeNotifier is active, then it will not remove itself from
+  // the old NetworkChangeNotifier which is a potential use-after-free.
+  resolver_ = nullptr;
   test::ScopedMockNetworkChangeNotifier notifier;
   CreateSerialResolver();  // To guarantee order of resolutions.
   resolver_->SetNoIPv6OnWifi(true);
 
   notifier.mock_network_change_notifier()->SetConnectionType(
       NetworkChangeNotifier::CONNECTION_WIFI);
   // Needed so IPv6 availability check isn't skipped.
   ChangeDnsConfig(CreateValidDnsConfig());
 
   proc_->AddRule("h1", ADDRESS_FAMILY_UNSPECIFIED, "::3");
@@ skipping 179 matching lines @@
   EXPECT_EQ(1, count2);
 
   // Make another request to make sure both callbacks were cleared.
   req = CreateRequest("just.testing", 80);
   EXPECT_THAT(req->Resolve(), IsOk());
   EXPECT_EQ(2, count1);
   EXPECT_EQ(1, count2);
 }
 
 }  // namespace net