Make the UI an observer of downloads.

chrome/browser/download/download_item_model.h

 // Copyright (c) 2012 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_ITEM_MODEL_H_
 #define CHROME_BROWSER_DOWNLOAD_DOWNLOAD_ITEM_MODEL_H_
 
 #include <string>
 
 #include "base/basictypes.h"
@@ skipping 72 matching lines @@
   bool IsMalicious() const;
 
   // Returns |true| if this download should be displayed in the downloads shelf.
   bool ShouldShowInShelf() const;
 
   // Change whether the download should be displayed on the downloads
   // shelf. Setting this is only effective if the download hasn't already been
   // displayed in the shelf.
   void SetShouldShowInShelf(bool should_show);
 
+  // Returns |true| if the UI should be notified when the download is ready to
+  // be presented in the UI. By default, this value is |false| and should be
+  // changed explicitly using SetShouldNotifyUI(). Note that this is indpendent
+  // of ShouldShowInShelf() since there might be actions other than showing in
+  // the shelf that the UI must perform.
+  bool ShouldNotifyUI() const;
+
+  // Change what's returned by ShouldNotifyUI().
+  void SetShouldNotifyUI(bool should_notify);
+
   content::DownloadItem* download() { return download_; }
 
  private:
   // Returns a string representations of the current download progress sizes. If
   // the total size of the download is known, this string looks like: "100/200
   // MB" where the numerator is the transferred size and the denominator is the
   // total size. If the total isn't known, returns the transferred size as a
   // string (e.g.: "100 MB").
   string16 GetProgressSizesString() const;
 
   // Returns a string indicating the status of an in-progress download.
   string16 GetInProgressStatusString() const;
 
   // The DownloadItem that this model represents. Note that DownloadItemModel
   // itself shouldn't maintain any state since there can be more than one
   // DownloadItemModel in use with the same DownloadItem.
   content::DownloadItem* download_;
 
   DISALLOW_COPY_AND_ASSIGN(DownloadItemModel);
 };
 
 #endif  // CHROME_BROWSER_DOWNLOAD_DOWNLOAD_ITEM_MODEL_H_