Reland 54771 (and 54795) To enable TCP Preconnection by default...

chrome/browser/net/predictor.h

 // Copyright (c) 2006-2010 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.
 
 // A Predictor object is instantiated once in the browser process, and manages
 // both preresolution of hostnames, as well as TCP/IP preconnection to expected
 // subresources.
 // Most hostname lists are provided by the renderer processes, and include URLs
 // that *might* be used in the near future by the browsing user.  One goal of
 // this class is to cause the underlying DNS structure to lookup a hostname
@@ skipping 65 matching lines @@
   // how long each has taken, etc. etc.  We also destroy records of suggesses
   // (cache hits etc.).
   void DiscardAllResults();
 
   // Add hostname(s) to the queue for processing.
   void ResolveList(const UrlList& urls,
                    UrlInfo::ResolutionMotivation motivation);
   void Resolve(const GURL& url,
                UrlInfo::ResolutionMotivation motivation);
 
-  // Instigate pre-connection to any URLs we predict will be needed after this
-  // navigation (typically more-embedded resources on a page).
+  // Instigate pre-connection to any URLs, or pre-resolution of related host,
+  // that we predict will be needed after this navigation (typically
+  // more-embedded resources on a page).  This method will actually post a task
+  // to do the actual work, so as not to jump ahead of the frame navigation that
+  // instigated this activity.
   void PredictFrameSubresources(const GURL& url);
 
   // Record details of a navigation so that we can preresolve the host name
   // ahead of time the next time the users navigates to the indicated host.
   void LearnFromNavigation(const GURL& referring_url, const GURL& target_url);
 
   // Dump HTML table containing list of referrers for about:dns.
   void GetHtmlReferrerLists(std::string* output);
 
   // Dump the list of currently known referrer domains and related prefetchable
@@ skipping 33 matching lines @@
   friend class base::RefCountedThreadSafe<Predictor>;
   FRIEND_TEST_ALL_PREFIXES(PredictorTest, BenefitLookupTest);
   FRIEND_TEST_ALL_PREFIXES(PredictorTest, ShutdownWhenResolutionIsPendingTest);
   FRIEND_TEST_ALL_PREFIXES(PredictorTest, SingleLookupTest);
   FRIEND_TEST_ALL_PREFIXES(PredictorTest, ConcurrentLookupTest);
   FRIEND_TEST_ALL_PREFIXES(PredictorTest, MassiveConcurrentLookupTest);
   FRIEND_TEST_ALL_PREFIXES(PredictorTest, PriorityQueuePushPopTest);
   FRIEND_TEST_ALL_PREFIXES(PredictorTest, PriorityQueueReorderTest);
   friend class WaitForResolutionHelper;  // For testing.
 
-  ~Predictor();
-
   class LookupRequest;
 
   // A simple priority queue for handling host names.
   // Some names that are queued up have |motivation| that requires very rapid
   // handling.  For example, a sub-resource name lookup MUST be done before the
   // actual sub-resource is fetched.  In contrast, a name that was speculatively
   // noted in a page has to be resolved before the user "gets around to"
   // clicking on a link.  By tagging (with a motivation) each push we make into
   // this FIFO queue, the queue can re-order the more important names to service
   // them sooner (relative to some low priority background resolutions).
@@ skipping 14 matching lines @@
     std::queue<GURL> background_queue_;
 
   DISALLOW_COPY_AND_ASSIGN(HostNameQueue);
   };
 
   // A map that is keyed with the host/port that we've learned were the cause
   // of loading additional URLs.  The list of additional targets is held
   // in a Referrer instance, which is a value in this map.
   typedef std::map<GURL, Referrer> Referrers;
 
+  ~Predictor();
+
+  // Perform actual resolution or preconnection to subresources now.  This is
+  // an internal worker method that is reached via a post task from
+  // PredictFrameSubresources().
+  void PrepareFrameSubresources(const GURL& url);
+
   // Only for testing. Returns true if hostname has been successfully resolved
   // (name found).
   bool WasFound(const GURL& url) const {
     Results::const_iterator it(results_.find(url));
     return (it != results_.end()) &&
             it->second.was_found();
   }
 
   // Only for testing. Return how long was the resolution
   // or UrlInfo::kNullDuration if it hasn't been resolved yet.
@@ skipping 68 matching lines @@
   // Are we currently using preconnection, rather than just DNS resolution, for
   // subresources and omni-box search URLs.
   bool preconnect_enabled_;
 
   DISALLOW_COPY_AND_ASSIGN(Predictor);
 };
 
 }  // namespace chrome_browser_net
 
 #endif  // CHROME_BROWSER_NET_PREDICTOR_H_