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 5bfc2bc4d502b698076f17c5160745a061895500..9de70ca0f4ff0b8e3ed93f5742700cea27d153cb 100644
--- a/chrome/browser/predictors/resource_prefetch_predictor.h
+++ b/chrome/browser/predictors/resource_prefetch_predictor.h
@@ -43,6 +43,19 @@ constexpr char kResourcePrefetchPredictorPrecisionHistogram[] =
     "ResourcePrefetchPredictor.LearningPrecision";
 constexpr char kResourcePrefetchPredictorRecallHistogram[] =
     "ResourcePrefetchPredictor.LearningRecall";
+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;
@@ -170,7 +183,8 @@ 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,
+                             const ResourcePrefetcher::PrefetcherStats& stats);
 
   // Returns true if prefetching data exists for the |main_frame_url|.
   virtual bool IsUrlPrefetchable(const GURL& main_frame_url);
@@ -216,7 +230,6 @@ class ResourcePrefetchPredictor
     INITIALIZING = 1,
     INITIALIZED = 2
   };
-
   typedef ResourcePrefetchPredictorTables::PrefetchDataMap PrefetchDataMap;
   typedef ResourcePrefetchPredictorTables::RedirectDataMap RedirectDataMap;
 
@@ -366,6 +379,8 @@ class ResourcePrefetchPredictor
 
   NavigationMap inflight_navigations_;
 
+  std::map<GURL, ResourcePrefetcher::PrefetcherStats> prefetcher_stats_;
+
   ScopedObserver<history::HistoryService, history::HistoryServiceObserver>
       history_service_observer_;
 
@@ -383,7 +398,9 @@ class TestObserver {
       size_t url_visit_count,
       const ResourcePrefetchPredictor::PageRequestSummary& summary) {}
 
-  virtual void OnPrefetchingFinished(const GURL& main_frame_url) {}
+  virtual void OnPrefetchingFinished(
+      const GURL& main_frame_url,
+      const ResourcePrefetcher::PrefetcherStats& stats) {}
 
   virtual void OnPredictorInitialized() {}