Reverting 19425.

Review URL: http://codereview.chromium.org/147242

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@19432 0039d316-1c4b-4281-b951-d872f2087c98

5 files changed, 31 insertions, 19 deletions

diff --git a/chrome/browser/net/chrome_url_request_context.cc b/chrome/browser/net/chrome_url_request_context.cc
index 4b788c5..1e01821 100644
--- a/chrome/browser/net/chrome_url_request_context.cc
+++ b/chrome/browser/net/chrome_url_request_context.cc
@@ -462,4 +462,7 @@ ChromeURLRequestContext::~ChromeURLRequestContext() {
   // it is owned by the original URLRequestContext.
   if (!is_off_the_record_ && !is_media_)
     delete proxy_service_;
+
+  // Do not delete host_resolver_; it will be freed by FreeGlobalHostResolver()
+  // during the teardown of DNS prefetching.
 }
diff --git a/chrome/browser/net/dns_global.cc b/chrome/browser/net/dns_global.cc
index 4b821c6..9e4c8f6 100644
--- a/chrome/browser/net/dns_global.cc
+++ b/chrome/browser/net/dns_global.cc
@@ -435,13 +435,9 @@ void InitDnsPrefetch(size_t max_concurrent, PrefService* user_prefs) {
 }
 
 void EnsureDnsPrefetchShutdown() {
-  if (NULL != dns_master) {
+  if (NULL != dns_master)
     dns_master->Shutdown();
-
-    // Stop observing DNS resolutions. Note that dns_master holds a reference
-    // to the global host resolver, so is guaranteed to be live.
-    GetGlobalHostResolver()->RemoveObserver(&dns_resolution_observer);
-  }
+  FreeGlobalHostResolver();
 }
 
 void FreeDnsPrefetchResources() {
@@ -473,6 +469,14 @@ net::HostResolver* GetGlobalHostResolver() {
   return global_host_resolver;
 }
 
+void FreeGlobalHostResolver() {
+  if (global_host_resolver) {
+    // Called from IO thread.
+    delete global_host_resolver;
+    global_host_resolver = NULL;
+  }
+}
+
 //------------------------------------------------------------------------------
 // Functions to handle saving of hostnames from one session to the next, to
 // expedite startup times.
diff --git a/chrome/browser/net/dns_global.h b/chrome/browser/net/dns_global.h
index e27062e..c9a864f 100644
--- a/chrome/browser/net/dns_global.h
+++ b/chrome/browser/net/dns_global.h
@@ -36,9 +36,13 @@ void EnsureDnsPrefetchShutdown();
 void FreeDnsPrefetchResources();
 
 // Lazily allocates a HostResolver to be used by the DNS prefetch system, on
-// the IO thread.
+// the IO thread. Must be matched by a call to FreeGlobalHostResolver().
 net::HostResolver* GetGlobalHostResolver();
 
+// Frees the HostResolver allocated by GetGlobalHostResolver(). Must be called
+// on the IO thread.
+void FreeGlobalHostResolver();
+
 //------------------------------------------------------------------------------
 // Global APIs relating to Prefetching in browser
 void EnableDnsPrefetch(bool enable);
diff --git a/chrome/browser/net/dns_master.h b/chrome/browser/net/dns_master.h
index 04fc56f..fa1c783 100644
--- a/chrome/browser/net/dns_master.h
+++ b/chrome/browser/net/dns_master.h
@@ -229,7 +229,7 @@ class DnsMaster : public base::RefCountedThreadSafe<DnsMaster> {
 
   // The host resovler we warm DNS entries for. The resolver (which is not
   // thread safe) should be accessed only on |host_resolver_loop_|.
-  scoped_refptr<net::HostResolver> host_resolver_;
+  net::HostResolver* host_resolver_;
   MessageLoop* host_resolver_loop_;
 
   DISALLOW_COPY_AND_ASSIGN(DnsMaster);
diff --git a/chrome/browser/net/dns_master_unittest.cc b/chrome/browser/net/dns_master_unittest.cc
index da720fe..e056555 100644
--- a/chrome/browser/net/dns_master_unittest.cc
+++ b/chrome/browser/net/dns_master_unittest.cc
@@ -82,6 +82,7 @@ class DnsMasterTest : public testing::Test {
     MessageLoop::current()->Run();
   }
 
+  net::HostResolver host_resolver_;
   scoped_refptr<net::RuleBasedHostMapper> mapper_;
 
  private:
@@ -110,10 +111,10 @@ static std::string GetNonexistantDomain() {
 TimeDelta BlockingDnsLookup(const std::string& hostname) {
     Time start = Time::Now();
 
-    scoped_refptr<net::HostResolver> resolver(new net::HostResolver);
+    net::HostResolver resolver;
     net::AddressList addresses;
     net::HostResolver::RequestInfo info(hostname, 80);
-    resolver->Resolve(info, &addresses, NULL, NULL);
+    resolver.Resolve(info, &addresses, NULL, NULL);
 
     return Time::Now() - start;
 }
@@ -162,13 +163,13 @@ TEST_F(DnsMasterTest, OsCachesLookupsTest) {
 }
 
 TEST_F(DnsMasterTest, StartupShutdownTest) {
-  scoped_refptr<DnsMaster> testing_master = new DnsMaster(new net::HostResolver,
+  scoped_refptr<DnsMaster> testing_master = new DnsMaster(&host_resolver_,
       MessageLoop::current(), DnsPrefetcherInit::kMaxConcurrentLookups);
   testing_master->Shutdown();
 }
 
 TEST_F(DnsMasterTest, BenefitLookupTest) {
-  scoped_refptr<DnsMaster> testing_master = new DnsMaster(new net::HostResolver,
+  scoped_refptr<DnsMaster> testing_master = new DnsMaster(&host_resolver_,
       MessageLoop::current(), DnsPrefetcherInit::kMaxConcurrentLookups);
 
   std::string goog("www.google.com"),
@@ -231,7 +232,7 @@ TEST_F(DnsMasterTest, ShutdownWhenResolutionIsPendingTest) {
   scoped_refptr<net::WaitingHostMapper> mapper = new net::WaitingHostMapper();
   net::ScopedHostMapper scoped_mapper(mapper.get());
 
-  scoped_refptr<DnsMaster> testing_master = new DnsMaster(new net::HostResolver,
+  scoped_refptr<DnsMaster> testing_master = new DnsMaster(&host_resolver_,
       MessageLoop::current(), DnsPrefetcherInit::kMaxConcurrentLookups);
 
   std::string localhost("127.0.0.1");
@@ -254,7 +255,7 @@ TEST_F(DnsMasterTest, ShutdownWhenResolutionIsPendingTest) {
 }
 
 TEST_F(DnsMasterTest, SingleLookupTest) {
-  scoped_refptr<DnsMaster> testing_master = new DnsMaster(new net::HostResolver,
+  scoped_refptr<DnsMaster> testing_master = new DnsMaster(&host_resolver_,
       MessageLoop::current(), DnsPrefetcherInit::kMaxConcurrentLookups);
 
   std::string goog("www.google.com");
@@ -283,7 +284,7 @@ TEST_F(DnsMasterTest, SingleLookupTest) {
 TEST_F(DnsMasterTest, ConcurrentLookupTest) {
   mapper_->AddSimulatedFailure("*.notfound");
 
-  scoped_refptr<DnsMaster> testing_master = new DnsMaster(new net::HostResolver,
+  scoped_refptr<DnsMaster> testing_master = new DnsMaster(&host_resolver_,
       MessageLoop::current(), DnsPrefetcherInit::kMaxConcurrentLookups);
 
   std::string goog("www.google.com"),
@@ -337,7 +338,7 @@ TEST_F(DnsMasterTest, ConcurrentLookupTest) {
 TEST_F(DnsMasterTest, DISABLED_MassiveConcurrentLookupTest) {
   mapper_->AddSimulatedFailure("*.notfound");
 
-  scoped_refptr<DnsMaster> testing_master = new DnsMaster(new net::HostResolver,
+  scoped_refptr<DnsMaster> testing_master = new DnsMaster(&host_resolver_,
       MessageLoop::current(), DnsPrefetcherInit::kMaxConcurrentLookups);
 
   NameList names;
@@ -441,7 +442,7 @@ int GetLatencyFromSerialization(const std::string& motivation,
 
 // Make sure nil referral lists really have no entries, and no latency listed.
 TEST_F(DnsMasterTest, ReferrerSerializationNilTest) {
-  scoped_refptr<DnsMaster> master = new DnsMaster(new net::HostResolver,
+  scoped_refptr<DnsMaster> master = new DnsMaster(&host_resolver_,
       MessageLoop::current(), DnsPrefetcherInit::kMaxConcurrentLookups);
   ListValue referral_list;
   master->SerializeReferrers(&referral_list);
@@ -456,7 +457,7 @@ TEST_F(DnsMasterTest, ReferrerSerializationNilTest) {
 // deserialized into the database, and can be extracted back out via
 // serialization without being changed.
 TEST_F(DnsMasterTest, ReferrerSerializationSingleReferrerTest) {
-  scoped_refptr<DnsMaster> master = new DnsMaster(new net::HostResolver,
+  scoped_refptr<DnsMaster> master = new DnsMaster(&host_resolver_,
       MessageLoop::current(), DnsPrefetcherInit::kMaxConcurrentLookups);
   std::string motivation_hostname = "www.google.com";
   std::string subresource_hostname = "icons.google.com";
@@ -480,7 +481,7 @@ TEST_F(DnsMasterTest, ReferrerSerializationSingleReferrerTest) {
 
 // Make sure the Trim() functionality works as expected.
 TEST_F(DnsMasterTest, ReferrerSerializationTrimTest) {
-  scoped_refptr<DnsMaster> master = new DnsMaster(new net::HostResolver,
+  scoped_refptr<DnsMaster> master = new DnsMaster(&host_resolver_,
       MessageLoop::current(), DnsPrefetcherInit::kMaxConcurrentLookups);
   std::string motivation_hostname = "www.google.com";
   std::string icon_subresource_hostname = "icons.google.com";