[net/dns] Suppress multiple DnsConfig withdrawals after timeout.

net/dns/dns_config_service_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_config_service.h"
 
 #include "base/basictypes.h"
 #include "base/bind.h"
 #include "base/cancelable_callback.h"
 #include "base/memory/scoped_ptr.h"
@@ skipping 96 matching lines @@
 
   service_->OnHostsRead(config.hosts);
   // Empty hosts is acceptable.
   EXPECT_TRUE(last_config_.IsValid());
   EXPECT_TRUE(last_config_.Equals(config));
 }
 
 TEST_F(DnsConfigServiceTest, Timeout) {
   DnsConfig config = MakeConfig(1);
   config.hosts = MakeHosts(1);
+  ASSERT_TRUE(config.IsValid());
 
   service_->OnConfigRead(config);
   service_->OnHostsRead(config.hosts);
   EXPECT_TRUE(last_config_.IsValid());
   EXPECT_TRUE(last_config_.Equals(config));
 
   service_->InvalidateConfig();
   WaitForConfig(TestTimeouts::action_timeout());
   EXPECT_FALSE(last_config_.IsValid());
 
   service_->OnConfigRead(config);
   EXPECT_TRUE(last_config_.Equals(config));
 
   service_->InvalidateHosts();
   WaitForConfig(TestTimeouts::action_timeout());
   EXPECT_FALSE(last_config_.IsValid());
 
+  service_->InvalidateConfig();
+  // We don't expect an update. This should time out. If we get an update,
+  // we'll detect unchanged config.
+  WaitForConfig(base::TimeDelta::FromMilliseconds(100) +
+                TestTimeouts::tiny_timeout());
+  EXPECT_FALSE(last_config_.IsValid());
+
+  service_->OnConfigRead(config);
   service_->OnHostsRead(config.hosts);
   EXPECT_TRUE(last_config_.Equals(config));
 }
 
 TEST_F(DnsConfigServiceTest, SameConfig) {
   DnsConfig config = MakeConfig(1);
   config.hosts = MakeHosts(1);
 
   service_->OnConfigRead(config);
   service_->OnHostsRead(config.hosts);
@@ skipping 47 matching lines @@
                            base::Unretained(this)));
   base::TimeDelta kTimeout = TestTimeouts::action_max_timeout();
   WaitForConfig(kTimeout);
   ASSERT_TRUE(last_config_.IsValid()) << "Did not receive DnsConfig in " <<
       kTimeout.InSecondsF() << "s";
 }
 #endif  // OS_POSIX || OS_WIN
 
 }  // namespace net