predictors: Add prefetching hit/miss histograms.

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 2af4be9e829da7e1e714545027667493b7ffbab3..05536a42434040b011407287319a3b055b356505 100644
--- a/chrome/browser/predictors/resource_prefetch_predictor.h
+++ b/chrome/browser/predictors/resource_prefetch_predictor.h
@@ -47,6 +47,18 @@ constexpr char kResourcePrefetchPredictorCountHistogram[] =
     "ResourcePrefetchPredictor.LearningCount";
 constexpr char kResourcePrefetchPredictorPrefetchingDurationHistogram[] =
     "ResourcePrefetchPredictor.PrefetchingDuration";
+constexpr char kResourcePrefetchPredictorPrefetchMissesCountCached[] =
+    "ResourcePrefetchPredictor.PrefetchMissesCount.Cached";
+constexpr char kResourcePrefetchPredictorPrefetchMissesCountNotCached[] =
+    "ResourcePrefetchPredictor.PrefetchMissesCount.NotCached";
+constexpr char kResourcePrefetchPredictorPrefetchHitsCountCached[] =
+    "ResourcePrefetchPredictor.PrefetchHitsCount.Cached";
+constexpr char kResourcePrefetchPredictorPrefetchHitsCountNotCached[] =
+    "ResourcePrefetchPredictor.PrefetchHitsCount.NotCached";
+constexpr char kResourcePrefetchPredictorPrefetchHitsSize[] =
+    "ResourcePrefetchPredictor.PrefetchHitsSizeKB";
+constexpr char kResourcePrefetchPredictorPrefetchMissesSize[] =
+    "ResourcePrefetchPredictor.PrefetchMissesSizeKB";
 }  // namespace internal
 
 class TestObserver;
@@ -174,7 +186,9 @@ class ResourcePrefetchPredictor
 
   // Called when ResourcePrefetcher is finished, i.e. there is nothing pending
   // in flight.
-  void OnPrefetchingFinished(const GURL& main_frame_url);
+  void OnPrefetchingFinished(
+      const GURL& main_frame_url,
+      std::unique_ptr<ResourcePrefetcher::PrefetcherStats> stats);
 
   // Returns true if prefetching data exists for the |main_frame_url|.
   virtual bool IsUrlPrefetchable(const GURL& main_frame_url);
@@ -222,7 +236,6 @@ class ResourcePrefetchPredictor
     INITIALIZING = 1,
     INITIALIZED = 2
   };
-
   typedef ResourcePrefetchPredictorTables::PrefetchDataMap PrefetchDataMap;
   typedef ResourcePrefetchPredictorTables::RedirectDataMap RedirectDataMap;
 
@@ -373,6 +386,9 @@ class ResourcePrefetchPredictor
   std::map<GURL, base::TimeTicks> inflight_prefetches_;
   NavigationMap inflight_navigations_;
 
+  std::map<GURL, std::unique_ptr<ResourcePrefetcher::PrefetcherStats>>
+      prefetcher_stats_;
+
   ScopedObserver<history::HistoryService, history::HistoryServiceObserver>
       history_service_observer_;