Track fraction of visits to top URLs.

chrome/browser/history/history_backend.h

Index: chrome/browser/history/history_backend.h
diff --git a/chrome/browser/history/history_backend.h b/chrome/browser/history/history_backend.h
index a55d6eb4b38e6613c2dff5c673b70e02e153a70f..dcf668790bcaaf865c6d48bba1489e1f628f81ff 100644
--- a/chrome/browser/history/history_backend.h
+++ b/chrome/browser/history/history_backend.h
@@ -578,6 +578,18 @@ class HistoryBackend : public base::RefCountedThreadSafe<HistoryBackend>,
 #if defined(OS_ANDROID)
   // Returns the name of android cache database.
   base::FilePath GetAndroidCacheFileName() const;
+
+  // Populate a map from a |MostVisitedURLList|. The map assigns a rank to each
+  // top URL and its redirects. This should only be done once at backend
+  // initialization.
+  // This can be removed for M31. (See issue 248761.)
+
+  void PopulateMostVisitedURLMap();
+  // Record counts of page visits by rank. If a url is not ranked, record the
+  // page visit in a slot corresponding to |max_top_url_count|, which should
+  // be one greater than the largest rank of any url in |top_urls|.
+  // This can be removed for M31. (See issue 248761.)
+  void RecordTopPageVisitStats(const GURL& url);
 #endif
 
   class URLQuerier;
@@ -909,6 +921,12 @@ class HistoryBackend : public base::RefCountedThreadSafe<HistoryBackend>,
 #if defined(OS_ANDROID)
   // Used to provide the Android ContentProvider APIs.
   scoped_ptr<AndroidProviderBackend> android_provider_backend_;
+
+  // Used to provide UMA on the number of page visits that are to the most
+  // visited URLs. This is here because the backend both has access to this
+  // information and is notified of page visits. The top sites service should
+  // be used instead whenever possible.
+  std::map<GURL, int> most_visited_urls_map_;
 #endif
 
   // Used to manage syncing of the typed urls datatype. This will be NULL