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..ff86eb13270e50106936e88883dd27de4a6377e5 100644
--- a/chrome/browser/history/download_database.h
+++ b/chrome/browser/history/download_database.h
@@ -34,7 +34,8 @@ 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);
+  bool UpdateDownload(int64 received_bytes, int32 state,
+                      const base::Time& end_time, DownloadID db_handle);
 
   // Update the path of one download. Returns true if successful.
   bool UpdateDownloadPath(const FilePath& path, DownloadID db_handle);
@@ -57,6 +58,9 @@ class DownloadDatabase {
   // all downloads that are in progress or are waiting to be cancelled.
   void RemoveDownloadsBetween(base::Time remove_begin, base::Time remove_end);
 
+  // Set the |opened| flag to true.
+  void MarkDownloadOpened(DownloadID db_handle);
+
  protected:
   // Returns the database for the functions in this interface.
   virtual sql::Connection& GetDB() = 0;
@@ -68,6 +72,25 @@ class DownloadDatabase {
   // would re-initialize it.
   bool DropDownloadTable();
 
+  bool MaybeUpgradeDownloadsSchema();
+
+  bool CreateDownloadsTable();
+
+  enum DownloadsSchemaVersion {
+    DOWNLOADS_SCHEMA_VERSION_UNINITIALIZED = -1,
+    DOWNLOADS_SCHEMA_VERSION_BASE = 0,
+    DOWNLOADS_SCHEMA_VERSION_OPENED = 1,
+    // Add new schema versions here with explicit numbers, update kCurrent, and
+    // support your new version in CreateDownloadsTable,
+    // MaybeUpgradeDownloadsSchema, and QueryDownloads.
+  };
+  static const DownloadsSchemaVersion kCurrentDownloadsSchemaVersion =
+    DOWNLOADS_SCHEMA_VERSION_OPENED;
+
+  DownloadsSchemaVersion downloads_schema_version() const {
+    return schema_version_;
+  }
+
  private:
   // TODO(rdsmith): Remove after http://crbug.com/96627 has been resolved.
   std::set<int64> returned_ids_;
@@ -76,6 +99,7 @@ class DownloadDatabase {
 
   int next_id_;
   sql::MetaTable meta_table_;
+  DownloadsSchemaVersion schema_version_;
 
   DISALLOW_COPY_AND_ASSIGN(DownloadDatabase);
 };