Port HistoryService::ScheduleDBTask to CancelableTaskTracker

chrome/browser/history/history_marshaling.h

Index: chrome/browser/history/history_marshaling.h
diff --git a/chrome/browser/history/history_marshaling.h b/chrome/browser/history/history_marshaling.h
index 546b12d65a0a89a4a737f4bf798ac3c7a3a47783..6cf6a415c8e8b67840598fb0d8df2077c335759e 100644
--- a/chrome/browser/history/history_marshaling.h
+++ b/chrome/browser/history/history_marshaling.h
@@ -25,14 +25,6 @@ typedef CancelableRequest1<HistoryService::QueryMostVisitedURLsCallback,
                            history::MostVisitedURLList>
     QueryMostVisitedURLsRequest;
 
-// Generic operations ---------------------------------------------------------
-
-// The argument here is an input value, which is the task to run on the
-// background thread. The callback is used to execute the portion of the task
-// that executes on the main thread.
-typedef CancelableRequest1<base::Closure, scoped_refptr<HistoryDBTask> >
-    HistoryDBTaskRequest;
-
 }  // namespace history
 
 #endif  // CHROME_BROWSER_HISTORY_HISTORY_MARSHALING_H_