Modified cancel and interrupt processing to avoid race with history.

chrome/browser/download/download_history.h

Index: chrome/browser/download/download_history.h
diff --git a/chrome/browser/download/download_history.h b/chrome/browser/download/download_history.h
index f4b48812137e7d34848e623cb39fb957f81e3e1d..1fea26b16492c3efdb9267879b1b295a338e3689 100644
--- a/chrome/browser/download/download_history.h
+++ b/chrome/browser/download/download_history.h
@@ -51,8 +51,10 @@ class DownloadHistory {
   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,
@@ -61,6 +63,10 @@ class DownloadHistory {
   // 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*> >