Adds speculative prefetching of resources.

chrome/browser/predictors/resource_prefetch_predictor.h

Index: chrome/browser/predictors/resource_prefetch_predictor.h
diff --git a/chrome/browser/predictors/resource_prefetch_predictor.h b/chrome/browser/predictors/resource_prefetch_predictor.h
index e5d71ed62dcecf04b069705ec5691be74cdc2c4b..f2cf6b5162d759f98c5c121fe6223287f028ff68 100644
--- a/chrome/browser/predictors/resource_prefetch_predictor.h
+++ b/chrome/browser/predictors/resource_prefetch_predictor.h
@@ -16,6 +16,7 @@
 #include "chrome/browser/history/history_types.h"
 #include "chrome/browser/predictors/resource_prefetch_common.h"
 #include "chrome/browser/predictors/resource_prefetch_predictor_tables.h"
+#include "chrome/browser/predictors/resource_prefetcher_manager.h"
 #include "chrome/browser/profiles/profile_keyed_service.h"
 #include "content/public/browser/notification_observer.h"
 #include "content/public/browser/notification_registrar.h"
@@ -52,40 +53,24 @@ namespace predictors {
 //   PredictorDatabase.
 // * ResourcePrefetchPredictor - Learns about resource requirements per URL in
 //   the UI thread through the ResourcePrefetchPredictorObserver and perisists
-//   it to disk in the DB thread through the ResourcePrefetchPredictorTables.
-//   Owned by profile.
+//   it to disk in the DB thread through the ResourcePrefetchPredictorTables. It
+//   initiates resource prefetching using the ResourcePrefetcherManager. Owned
+//   by profile.
+// * ResourcePrefetcherManager - Manages the ResourcePrefetchers that do the
+//   prefetching on the IO thread. The manager is owned by the
+//   ResourcePrefetchPredictor and interfaces between the predictor on the UI
+//   thread and the prefetchers on the IO thread.
+// * ResourcePrefetcher - Lives entirely on the IO thread, owned by the
+//   ResourcePrefetcherManager, and issues net::URLRequest to fetch resources.
 //
-// TODO(shishir): Implement the prefetching of resources.
 // TODO(shishir): Do speculative prefetching for https resources and/or https
 // main_frame urls.
 class ResourcePrefetchPredictor
     : public ProfileKeyedService,
       public content::NotificationObserver,
+      public ResourcePrefetcherManager::Delegate,

[dominich, 2012/07/23 16:04:41]

do you really need the delegate pattern here? Consider having an explicit
dependency between the Manager and the Predictor.

[Shishir, 2012/08/01 22:35:24]

Done.

       public base::SupportsWeakPtr<ResourcePrefetchPredictor> {
  public:
-  // The following config allows us to change the predictor constants and run
-  // field trials with different constants.
-  struct Config {
-    // Initializes the config with default values.
-    Config();
-
-    // If a navigation hasn't seen a load complete event in this much time, it
-    // is considered abandoned.
-    int max_navigation_lifetime_seconds;  // Default 60
-    // Size of LRU caches for the Url data.
-    size_t max_urls_to_track;  // Default 500
-    // The number of times, we should have seen a visit to this Url in history
-    // to start tracking it. This is to ensure we dont bother with oneoff
-    // entries.
-    int min_url_visit_count;  // Default 3
-    // The maximum number of resources to store per entry.
-    int max_resources_per_entry;  // Default 50
-    // The number of consecutive misses after we stop tracking a resource Url.
-    int max_consecutive_misses;  // Default 3
-    // The number of resources we should report accuracy stats on.
-    int num_resources_assumed_prefetched;  // Default 25
-  };
-
   // Stores the data that we need to get from the URLRequest.
   struct URLRequestSummary {
     URLRequestSummary();
@@ -101,11 +86,11 @@ class ResourcePrefetchPredictor
     bool was_cached;
   };
 
-  ResourcePrefetchPredictor(const Config& config, Profile* profile);
+  ResourcePrefetchPredictor(const ResourcePrefetchPredictorConfig& config,
+                            Profile* profile);
   virtual ~ResourcePrefetchPredictor();
 
   // Thread safe.
-  static bool IsEnabled(Profile* profile);
   static bool ShouldRecordRequest(net::URLRequest* request,
                                   ResourceType::Type resource_type);
   static bool ShouldRecordResponse(net::URLRequest* response);
@@ -159,12 +144,19 @@ class ResourcePrefetchPredictor
 
   typedef std::map<NavigationID, std::vector<URLRequestSummary> > NavigationMap;
   typedef std::map<GURL, UrlTableCacheValue> UrlTableCacheMap;
+  typedef std::map<NavigationID, linked_ptr<ResourcePrefetcher::RequestVector> >

[dominich, 2012/07/23 16:04:41]

red flag: linked_ptr is unlikely to be what you want. Why isn't this just a
vector pointer? Can a single RequestVector be the value for multiple
NavigationID keys? If so, this is the wrong data structure to use.

[Shishir, 2012/08/01 22:35:24]

Changed to plain pointers.

+      ResultsMap;
 
   // content::NotificationObserver methods OVERRIDE.
   virtual void Observe(int type,
                        const content::NotificationSource& source,
                        const content::NotificationDetails& details) OVERRIDE;
 
+  // ResourcePrefetcherManager::Delegate methods OVERRIDE.
+  virtual void FinishedPrefetchForNavigation(
+      const NavigationID& navigation_id,
+      scoped_ptr<ResourcePrefetcher::RequestVector> requests) OVERRIDE;
+
   static bool IsHandledMainPage(net::URLRequest* request);
   static bool IsHandledSubresource(net::URLRequest* response);
   static bool IsCacheable(const net::URLRequest* response);
@@ -194,19 +186,24 @@ class ResourcePrefetchPredictor
   void OnNavigationComplete(const NavigationID& navigation_id);
   void LearnUrlNavigation(const GURL& main_frame_url,
                           const std::vector<URLRequestSummary>& new_value);
-  void MaybeReportAccuracyStats(const NavigationID& navigation_id) const;
+
+  void MaybeReportAccuracyStats(const NavigationID& navigation_id);
+  void MaybeReportSimulatedAccuracyStats(
+      const NavigationID& navigation_id) const;
 
   void SetTablesForTesting(
       scoped_refptr<ResourcePrefetchPredictorTables> tables);
 
   Profile* const profile_;
-  Config config_;
+  ResourcePrefetchPredictorConfig config_;

[dominich, 2012/07/23 16:04:41]

const?

[Shishir, 2012/08/01 22:35:24]

Done.

   InitializationState initialization_state_;
   scoped_refptr<ResourcePrefetchPredictorTables> tables_;
+  scoped_refptr<ResourcePrefetcherManager> prefetch_manager_;

[dominich, 2012/07/23 16:04:41]

Why is this a refptr? I'm surprised there can be more than one instance. Maybe
it should be ProfileKeyed?

[Shishir, 2012/08/01 22:35:24]

Needs to be refcounted because it needs to be accessed both on UI and IO
threads. 
It can be profile keyed, but I dont see the point since it is only used by this
class right now which is profile keyed.

   content::NotificationRegistrar notification_registrar_;
 
   NavigationMap inflight_navigations_;
   UrlTableCacheMap url_table_cache_;
+  ResultsMap results_map_;
 
   DISALLOW_COPY_AND_ASSIGN(ResourcePrefetchPredictor);
 };