Make net::HostResolver refcounted.

This way it can be properly shared between the url request contexts, and the dns prefetcher, and dns observer.

BUG=http://crbug.com/14664
TEST=existing unit tests.

Review URL: http://codereview.chromium.org/149053

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@19425 0039d316-1c4b-4281-b951-d872f2087c98

5 files changed, 19 insertions, 31 deletions

diff --git a/chrome/browser/net/chrome_url_request_context.cc b/chrome/browser/net/chrome_url_request_context.cc
index 1e01821..4b788c5 100644
--- a/chrome/browser/net/chrome_url_request_context.cc
+++ b/chrome/browser/net/chrome_url_request_context.cc
@@ -462,7 +462,4 @@ 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 9e4c8f6..4b821c6 100644
--- a/chrome/browser/net/dns_global.cc
+++ b/chrome/browser/net/dns_global.cc
@@ -435,9 +435,13 @@ void InitDnsPrefetch(size_t max_concurrent, PrefService* user_prefs) {
 }
 
 void EnsureDnsPrefetchShutdown() {
-  if (NULL != dns_master)
+  if (NULL != dns_master) {
     dns_master->Shutdown();
-  FreeGlobalHostResolver();
+
+    // 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);
+  }
 }
 
 void FreeDnsPrefetchResources() {
@@ -469,14 +473,6 @@ 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 c9a864f..e27062e 100644
--- a/chrome/browser/net/dns_global.h
+++ b/chrome/browser/net/dns_global.h
@@ -36,13 +36,9 @@ void EnsureDnsPrefetchShutdown();
 void FreeDnsPrefetchResources();
 
 // Lazily allocates a HostResolver to be used by the DNS prefetch system, on
-// the IO thread. Must be matched by a call to FreeGlobalHostResolver().
+// the IO thread.
 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 fa1c783..04fc56f 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_|.
-  net::HostResolver* host_resolver_;
+  scoped_refptr<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 e056555..da720fe 100644
--- a/chrome/browser/net/dns_master_unittest.cc
+++ b/chrome/browser/net/dns_master_unittest.cc
@@ -82,7 +82,6 @@ class DnsMasterTest : public testing::Test {
     MessageLoop::current()->Run();
   }
 
-  net::HostResolver host_resolver_;
   scoped_refptr<net::RuleBasedHostMapper> mapper_;
 
  private:
@@ -111,10 +110,10 @@ static std::string GetNonexistantDomain() {
 TimeDelta BlockingDnsLookup(const std::string& hostname) {
     Time start = Time::Now();
 
-    net::HostResolver resolver;
+    scoped_refptr<net::HostResolver> resolver(new net::HostResolver);
     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;
 }
@@ -163,13 +162,13 @@ TEST_F(DnsMasterTest, OsCachesLookupsTest) {
 }
 
 TEST_F(DnsMasterTest, StartupShutdownTest) {
-  scoped_refptr<DnsMaster> testing_master = new DnsMaster(&host_resolver_,
+  scoped_refptr<DnsMaster> testing_master = new DnsMaster(new net::HostResolver,
       MessageLoop::current(), DnsPrefetcherInit::kMaxConcurrentLookups);
   testing_master->Shutdown();
 }
 
 TEST_F(DnsMasterTest, BenefitLookupTest) {
-  scoped_refptr<DnsMaster> testing_master = new DnsMaster(&host_resolver_,
+  scoped_refptr<DnsMaster> testing_master = new DnsMaster(new net::HostResolver,
       MessageLoop::current(), DnsPrefetcherInit::kMaxConcurrentLookups);
 
   std::string goog("www.google.com"),
@@ -232,7 +231,7 @@ 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(&host_resolver_,
+  scoped_refptr<DnsMaster> testing_master = new DnsMaster(new net::HostResolver,
       MessageLoop::current(), DnsPrefetcherInit::kMaxConcurrentLookups);
 
   std::string localhost("127.0.0.1");
@@ -255,7 +254,7 @@ TEST_F(DnsMasterTest, ShutdownWhenResolutionIsPendingTest) {
 }
 
 TEST_F(DnsMasterTest, SingleLookupTest) {
-  scoped_refptr<DnsMaster> testing_master = new DnsMaster(&host_resolver_,
+  scoped_refptr<DnsMaster> testing_master = new DnsMaster(new net::HostResolver,
       MessageLoop::current(), DnsPrefetcherInit::kMaxConcurrentLookups);
 
   std::string goog("www.google.com");
@@ -284,7 +283,7 @@ TEST_F(DnsMasterTest, SingleLookupTest) {
 TEST_F(DnsMasterTest, ConcurrentLookupTest) {
   mapper_->AddSimulatedFailure("*.notfound");
 
-  scoped_refptr<DnsMaster> testing_master = new DnsMaster(&host_resolver_,
+  scoped_refptr<DnsMaster> testing_master = new DnsMaster(new net::HostResolver,
       MessageLoop::current(), DnsPrefetcherInit::kMaxConcurrentLookups);
 
   std::string goog("www.google.com"),
@@ -338,7 +337,7 @@ TEST_F(DnsMasterTest, ConcurrentLookupTest) {
 TEST_F(DnsMasterTest, DISABLED_MassiveConcurrentLookupTest) {
   mapper_->AddSimulatedFailure("*.notfound");
 
-  scoped_refptr<DnsMaster> testing_master = new DnsMaster(&host_resolver_,
+  scoped_refptr<DnsMaster> testing_master = new DnsMaster(new net::HostResolver,
       MessageLoop::current(), DnsPrefetcherInit::kMaxConcurrentLookups);
 
   NameList names;
@@ -442,7 +441,7 @@ 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(&host_resolver_,
+  scoped_refptr<DnsMaster> master = new DnsMaster(new net::HostResolver,
       MessageLoop::current(), DnsPrefetcherInit::kMaxConcurrentLookups);
   ListValue referral_list;
   master->SerializeReferrers(&referral_list);
@@ -457,7 +456,7 @@ 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(&host_resolver_,
+  scoped_refptr<DnsMaster> master = new DnsMaster(new net::HostResolver,
       MessageLoop::current(), DnsPrefetcherInit::kMaxConcurrentLookups);
   std::string motivation_hostname = "www.google.com";
   std::string subresource_hostname = "icons.google.com";
@@ -481,7 +480,7 @@ TEST_F(DnsMasterTest, ReferrerSerializationSingleReferrerTest) {
 
 // Make sure the Trim() functionality works as expected.
 TEST_F(DnsMasterTest, ReferrerSerializationTrimTest) {
-  scoped_refptr<DnsMaster> master = new DnsMaster(&host_resolver_,
+  scoped_refptr<DnsMaster> master = new DnsMaster(new net::HostResolver,
       MessageLoop::current(), DnsPrefetcherInit::kMaxConcurrentLookups);
   std::string motivation_hostname = "www.google.com";
   std::string icon_subresource_hostname = "icons.google.com";