[Downloads] Remove unmapped histograms.

components/history/core/browser/history_backend.cc

Index: components/history/core/browser/history_backend.cc
diff --git a/components/history/core/browser/history_backend.cc b/components/history/core/browser/history_backend.cc
index 9b17ed6a8af7b9255d3e974886bd32b48b2a853b..166921d35f49382abad71db0023e596e36b0f9c5 100644
--- a/components/history/core/browser/history_backend.cc
+++ b/components/history/core/browser/history_backend.cc
@@ -1221,10 +1221,6 @@ void HistoryBackend::RemoveDownloads(const std::set<uint32_t>& ids) {
                         (1000 * micros) / num_downloads_deleted);
   }
   DCHECK_GE(ids.size(), num_downloads_deleted);
-  if (ids.size() < num_downloads_deleted)
-    return;
-  UMA_HISTOGRAM_COUNTS("Download.DatabaseRemoveDownloadsCountNotRemoved",
-                       ids.size() - num_downloads_deleted);
 }
 
 void HistoryBackend::QueryHistory(const base::string16& text_query,