Shift passage of FileStream in downloads system to be by scoped_ptr<>.

content/browser/download/download_file_manager.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.
 
 #include "content/browser/download/download_file_manager.h"
 
 #include <set>
 #include <string>
 
 #include "base/bind.h"
@@ skipping 45 matching lines @@
 void DownloadFileManager::CreateDownloadFile(
     scoped_ptr<DownloadCreateInfo> info,
     scoped_ptr<content::ByteStreamReader> stream,
     scoped_refptr<DownloadManager> download_manager, bool get_hash,
     const net::BoundNetLog& bound_net_log,
     const CreateDownloadFileCallback& callback) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
   DCHECK(info.get());
   VLOG(20) << __FUNCTION__ << "()" << " info = " << info->DebugString();
 
+  DownloadId id(info->download_id);

[benjhayden, 2012/10/11 19:41:12]

Comment that we can't use |info| after we Pass() it away?

Is there any way to tell the compiler "Please throw an error if I use this
variable again after I Pass() it away"?

[Randy Smith (Not in Mondays), 2012/10/15 18:56:32]

Done.
Might be doable with a clang plugin, but I don't think without that.  You'd need
a full dataflow analysis of that section of code, which is a bit tricky for
compilers to do.

+
   scoped_ptr<DownloadFile> download_file(download_file_factory_->CreateFile(
-      info.get(), stream.Pass(), download_manager, get_hash, bound_net_log));
+      info.Pass(), stream.Pass(), download_manager, get_hash, bound_net_log));
 
   content::DownloadInterruptReason interrupt_reason(
       download_file->Initialize());
   if (interrupt_reason == content::DOWNLOAD_INTERRUPT_REASON_NONE) {
-    DCHECK(GetDownloadFile(info->download_id) == NULL);
-    downloads_[info->download_id] = download_file.release();
+    DCHECK(GetDownloadFile(id) == NULL);
+    downloads_[id] = download_file.release();
   }
 
   BrowserThread::PostTask(BrowserThread::UI, FROM_HERE,
                           base::Bind(callback, interrupt_reason));
 }
 
 DownloadFile* DownloadFileManager::GetDownloadFile(
     DownloadId global_id) {
   DownloadFileMap::iterator it = downloads_.find(global_id);
   return it == downloads_.end() ? NULL : it->second;
@@ skipping 90 matching lines @@
   DownloadFile* download_file = downloads_[global_id];
 
   VLOG(20) << " " << __FUNCTION__ << "()"
            << " id = " << global_id
            << " download_file = " << download_file->DebugString();
 
   downloads_.erase(global_id);
 
   delete download_file;
 }