Add new UMA stats to get a handle on Downloads UI Usage

chrome/browser/history/download_database.h

Index: chrome/browser/history/download_database.h
diff --git a/chrome/browser/history/download_database.h b/chrome/browser/history/download_database.h
index 1d5d3fde9de3c1d361aeb0e86b45b3d12061ab2f..e72ddb5a05e839227defc38d82de79da8647e646 100644
--- a/chrome/browser/history/download_database.h
+++ b/chrome/browser/history/download_database.h
@@ -7,6 +7,7 @@
 #pragma once
 
 #include <set>
+#include <string>
 
 #include "base/threading/platform_thread.h"
 #include "chrome/browser/history/history_types.h"
@@ -34,7 +35,9 @@ class DownloadDatabase {
   void QueryDownloads(std::vector<DownloadPersistentStoreInfo>* results);
 
   // Update the state of one download. Returns true if successful.
-  bool UpdateDownload(int64 received_bytes, int32 state, DownloadID db_handle);
+  // Does not update |url|, |start_time|, |total_bytes|; uses |db_handle| only
+  // to select the row in the database table to update.
+  bool UpdateDownload(const DownloadPersistentStoreInfo& data);
 
   // Update the path of one download. Returns true if successful.
   bool UpdateDownloadPath(const FilePath& path, DownloadID db_handle);
@@ -69,6 +72,8 @@ class DownloadDatabase {
   bool DropDownloadTable();
 
  private:
+  bool EnsureColumnExists(const std::string& name, const std::string& type);
+
   // TODO(rdsmith): Remove after http://crbug.com/96627 has been resolved.
   std::set<int64> returned_ids_;
   bool owning_thread_set_;