Modified cancel and interrupt processing to avoid race with history.

chrome/browser/download/download_history.h

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CHROME_BROWSER_DOWNLOAD_DOWNLOAD_HISTORY_H_
 #define CHROME_BROWSER_DOWNLOAD_DOWNLOAD_HISTORY_H_
 #pragma once
 
 #include <map>
 
@@ skipping 33 matching lines @@
   void AddEntry(DownloadItem* download_item,
                 HistoryService::DownloadCreateCallback* callback);
 
   // Updates the history entry for |download_item|.
   void UpdateEntry(DownloadItem* download_item);
 
   // Updates the download path for |download_item| to |new_path|.
   void UpdateDownloadPath(DownloadItem* download_item,
                           const FilePath& new_path);
 
-  // Removes |download_item| from the history database.
-  void RemoveEntry(DownloadItem* download_item);
+  // Removes the download identified by |db_handle| from the history database.
+  // |db_handle| is used instead of the DownloadItem pointer to allow
+  // removal after deletion of the download item.
+  void RemoveEntry(int64 db_handle);

[Randy Smith (Not in Mondays), 2011/06/30 23:05:13]

Go over DownloadHistory interface; how "strange" is the use of db_handle?  Any
way to avoid that?  Maybe switch the whole thing over to db_handle?  Explore
options.

[Randy Smith (Not in Mondays), 2011/07/05 20:28:44]

Hmmm.  AddEntry and UpdateEntry sorta need the download item, because that's
what the entry is created based on (though we could hoist DownloadHistoryInfo up
a level if we wanted).  UpdateDownloadPath could get transferred over.  I think
I'll leave it like it is (a bit of a mess) until we've updated the ID behavior.

 
   // Removes download-related history entries in the given time range.
   void RemoveEntriesBetween(const base::Time remove_begin,
                             const base::Time remove_end);
 
   // Returns a new unique database handle which will not collide with real ones.
   int64 GetNextFakeDbHandle();
 
+  // Returns whether a given handle is fake.  True for
+  // kUninitializedHandle and all returns from GetNextFakeDbHandle().
+  static bool IsFakeHandle(int64 db_handle);
+
  private:
   typedef std::map<HistoryService::Handle,
                    std::pair<int32, VisitedBeforeDoneCallback*> >
       VisitedBeforeRequestsMap;
 
   void OnGotVisitCountToHost(HistoryService::Handle handle,
                              bool found_visits,
                              int count,
                              base::Time first_visit);
 
   Profile* profile_;
 
   // In case we don't have a valid db_handle, we use |fake_db_handle_| instead.
   // This is useful for incognito mode or when the history database is offline.
   // Downloads are expected to have unique handles, so we decrement the next
   // fake handle value on every use.
   int64 next_fake_db_handle_;
 
   CancelableRequestConsumer history_consumer_;
 
   // The outstanding requests made by CheckVisitedReferrerBefore().
   VisitedBeforeRequestsMap visited_before_requests_;
 
   DISALLOW_COPY_AND_ASSIGN(DownloadHistory);
 };
 
 #endif  // CHROME_BROWSER_DOWNLOAD_DOWNLOAD_HISTORY_H_