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

content/browser/download/download_file_manager.cc

Index: content/browser/download/download_file_manager.cc
diff --git a/content/browser/download/download_file_manager.cc b/content/browser/download/download_file_manager.cc
index 7577208cf20139e4b2942b230b6cc5bc71d5b035..3242a933fa6949a13a36b8e9687a8b7caa0790d7 100644
--- a/content/browser/download/download_file_manager.cc
+++ b/content/browser/download/download_file_manager.cc
@@ -63,14 +63,16 @@ void DownloadFileManager::CreateDownloadFile(
   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,