Seventh patch in making destructors of refcounted objects private.

BUG=26749
Review URL: http://codereview.chromium.org/371006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@31192 0039d316-1c4b-4281-b951-d872f2087c98
diff --git a/chrome/browser/net/dns_master.h b/chrome/browser/net/dns_master.h
index 451e9ed9..8309789 100644
--- a/chrome/browser/net/dns_master.h
+++ b/chrome/browser/net/dns_master.h
@@ -44,7 +44,6 @@
   // |host_resolver| instance.
   DnsMaster(net::HostResolver* host_resolver,
             TimeDelta max_queue_delay_ms, size_t max_concurrent);
-  ~DnsMaster();
 
   // Cancel pending requests and prevent new ones from being made.
   void Shutdown();
@@ -101,6 +100,7 @@
   size_t max_concurrent_lookups() const { return max_concurrent_lookups_; }
 
  private:
+  friend class base::RefCountedThreadSafe<DnsMaster>;
   FRIEND_TEST(DnsMasterTest, BenefitLookupTest);
   FRIEND_TEST(DnsMasterTest, ShutdownWhenResolutionIsPendingTest);
   FRIEND_TEST(DnsMasterTest, SingleLookupTest);
@@ -110,6 +110,8 @@
   FRIEND_TEST(DnsMasterTest, PriorityQueueReorderTest);
   friend class WaitForResolutionHelper;  // For testing.
 
+  ~DnsMaster();
+
   class LookupRequest;
 
   // A simple priority queue for handling host names.