predictors: move ResourcePrefetcher handling to LoadingPredictor.

chrome/browser/predictors/resource_prefetcher.h

 // Copyright 2014 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.
 
 #ifndef CHROME_BROWSER_PREDICTORS_RESOURCE_PREFETCHER_H_
 #define CHROME_BROWSER_PREDICTORS_RESOURCE_PREFETCHER_H_
 
 #include <stddef.h>
 
 #include <list>
 #include <map>
 #include <memory>
 #include <string>
 #include <utility>
 #include <vector>
 
 #include "base/macros.h"
+#include "base/memory/ptr_util.h"
 #include "base/threading/thread_checker.h"
 #include "base/time/time.h"
 #include "net/url_request/redirect_info.h"
 #include "net/url_request/url_request.h"
+#include "net/url_request/url_request_context_getter.h"
 #include "url/gurl.h"
 
-namespace net {
-class URLRequestContext;
-}
-
 namespace predictors {
 
 namespace internal {
 constexpr char kResourcePrefetchPredictorCachePatternHistogram[] =
     "ResourcePrefetchPredictor.CachePattern";
 constexpr char kResourcePrefetchPredictorPrefetchedCountHistogram[] =
     "ResourcePrefetchPredictor.PrefetchedCount";
 constexpr char kResourcePrefetchPredictorPrefetchedSizeHistogram[] =
     "ResourcePrefetchPredictor.PrefetchedSizeKB";
 }  // namespace internal
 
 // Responsible for prefetching resources for a single main frame URL based on
 // the input list of resources.
 //  - Limits the max number of resources in flight for any host and also across
 //    hosts.
 //  - When stopped, will wait for the pending requests to finish.
-//  - Lives entirely on the IO thread.
+//  - Created on the UI thread, member functions called and instances destroyed
+//    on the IO thread.
 class ResourcePrefetcher : public net::URLRequest::Delegate {
  public:
   struct PrefetchedRequestStats {
     PrefetchedRequestStats(const GURL& resource_url,
                            bool was_cached,
                            size_t total_received_bytes);
     ~PrefetchedRequestStats();
 
     GURL resource_url;
     bool was_cached;
     size_t total_received_bytes;
   };
 
   struct PrefetcherStats {
     explicit PrefetcherStats(const GURL& url);
     ~PrefetcherStats();
     PrefetcherStats(const PrefetcherStats& other);
 
     GURL url;
     base::TimeTicks start_time;
     std::vector<PrefetchedRequestStats> requests_stats;
   };
 
-  // Used to communicate when the prefetching is done. All methods are invoked
-  // on the IO thread.
+  // Used to communicate when the prefetching is done. Lives on the UI thread.
   class Delegate {
    public:
-    virtual ~Delegate() { }
+    virtual ~Delegate() {}
 
     // Called when the ResourcePrefetcher is finished, i.e. there is nothing
     // pending in flight.
     virtual void ResourcePrefetcherFinished(
         ResourcePrefetcher* prefetcher,
         std::unique_ptr<PrefetcherStats> stats) = 0;
-
-    virtual net::URLRequestContext* GetURLRequestContext() = 0;
   };
 
-  // |delegate| has to outlive the ResourcePrefetcher.
-  ResourcePrefetcher(Delegate* delegate,
+  ResourcePrefetcher(base::WeakPtr<Delegate> delegate,
+                     scoped_refptr<net::URLRequestContextGetter> context_getter,
                      size_t max_concurrent_requests,
                      size_t max_concurrent_requests_per_host,
                      const GURL& main_frame_url,
                      const std::vector<GURL>& urls);
   ~ResourcePrefetcher() override;
 
   void Start();  // Kicks off the prefetching. Can only be called once.
   void Stop();   // No additional prefetches will be queued after this.
 
   const GURL& main_frame_url() const { return main_frame_url_; }
@@ skipping 37 matching lines @@
   void OnResponseStarted(net::URLRequest* request, int net_error) override;
   void OnReadCompleted(net::URLRequest* request, int bytes_read) override;
 
   enum PrefetcherState {
     INITIALIZED = 0,  // Prefetching hasn't started.
     RUNNING = 1,      // Prefetching started, allowed to add more requests.
     STOPPED = 2,      // Prefetching started, not allowed to add more requests.
     FINISHED = 3      // No more inflight request, new requests not possible.
   };
 
-  base::ThreadChecker thread_checker_;
   PrefetcherState state_;
-  Delegate* const delegate_;
+  base::WeakPtr<Delegate> delegate_;
+  scoped_refptr<net::URLRequestContextGetter> context_getter_;
   size_t max_concurrent_requests_;
   size_t max_concurrent_requests_per_host_;
   GURL main_frame_url_;
 
   // For histogram reports.
   size_t prefetched_count_;
   int64_t prefetched_bytes_;
 
   std::map<net::URLRequest*, std::unique_ptr<net::URLRequest>>
       inflight_requests_;
   std::list<GURL> request_queue_;
   std::map<std::string, size_t> host_inflight_counts_;
   std::unique_ptr<PrefetcherStats> stats_;
 
   DISALLOW_COPY_AND_ASSIGN(ResourcePrefetcher);
 };
 
 }  // namespace predictors
 
 #endif  // CHROME_BROWSER_PREDICTORS_RESOURCE_PREFETCHER_H_