predictors: Add prefetching hit/miss histograms.

chrome/browser/predictors/resource_prefetcher_manager.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_MANAGER_H_
 #define CHROME_BROWSER_PREDICTORS_RESOURCE_PREFETCHER_MANAGER_H_
 
 #include <map>
 #include <memory>
 #include <string>
@@ skipping 37 matching lines @@
   // Will create a new ResourcePrefetcher for a given main frame url if there
   // isn't one already for the same host.
   void MaybeAddPrefetch(const GURL& main_frame_url,
                         const std::vector<GURL>& urls);
 
   // Stops the ResourcePrefetcher for a given main frame URL, if one was in
   // progress.
   void MaybeRemovePrefetch(const GURL& main_frame_url);
 
   // ResourcePrefetcher::Delegate methods.
-  void ResourcePrefetcherFinished(ResourcePrefetcher* prefetcher) override;
+  void ResourcePrefetcherFinished(
+      ResourcePrefetcher* prefetcher,
+      std::unique_ptr<ResourcePrefetcher::PrefetcherStats> stats) override;
   net::URLRequestContext* GetURLRequestContext() override;
 
  private:
   friend class base::RefCountedThreadSafe<ResourcePrefetcherManager>;
   friend class MockResourcePrefetcherManager;
 
   ~ResourcePrefetcherManager() override;
 
   ResourcePrefetchPredictor* predictor_;
   const ResourcePrefetchPredictorConfig config_;
   net::URLRequestContextGetter* const context_getter_;
 
   std::map<std::string, std::unique_ptr<ResourcePrefetcher>> prefetcher_map_;
 
   DISALLOW_COPY_AND_ASSIGN(ResourcePrefetcherManager);
 };
 
 }  // namespace predictors
 
 #endif  // CHROME_BROWSER_PREDICTORS_RESOURCE_PREFETCHER_MANAGER_H_