Make the UI an observer of downloads.

content/browser/download/download_item_impl.cc

 // 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.
 
 // File method ordering: Methods in this file are in the same order as
 // in download_item_impl.h, with the following exception: The public
 // interface Start is placed in chronological order with the other
 // (private) routines that together define a DownloadItem's state
 // transitions as the download progresses.  See "Download progression
 // cascade" later in this file.
@@ skipping 1026 matching lines @@
 
 void DownloadItemImpl::OnDownloadRenamedToIntermediateName(
     DownloadInterruptReason reason,
     const FilePath& full_path) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
   VLOG(20) << __FUNCTION__ << " download=" << DebugString(true);
   if (DOWNLOAD_INTERRUPT_REASON_NONE != reason)
     Interrupt(reason);
   else
     SetFullPath(full_path);
-  delegate_->ShowDownloadInBrowser(this);
 
   MaybeCompleteDownload();
 }
 
 // When SavePackage downloads MHTML to GData (see
 // SavePackageFilePickerChromeOS), GData calls MaybeCompleteDownload() like it
 // does for non-SavePackage downloads, but SavePackage downloads never satisfy
 // IsDownloadReadyForCompletion(). GDataDownloadObserver manually calls
 // DownloadItem::UpdateObservers() when the upload completes so that SavePackage
 // notices that the upload has completed and runs its normal Finish() pathway.
@@ skipping 355 matching lines @@
       return "CANCELLED";
     case INTERRUPTED_INTERNAL:
       return "INTERRUPTED";
     default:
       NOTREACHED() << "Unknown download state " << state;
       return "unknown";
   };
 }
 
 }  // namespace content