URLFetcher won't call delegate until file is closed.

net/url_request/url_fetcher_response_writer.cc

Index: net/url_request/url_fetcher_response_writer.cc
diff --git a/net/url_request/url_fetcher_response_writer.cc b/net/url_request/url_fetcher_response_writer.cc
index cb30dad8089efd6acd2d699126782cce3d147c45..d2f42370b3644f452e592b11310edf6c3c04634f 100644
--- a/net/url_request/url_fetcher_response_writer.cc
+++ b/net/url_request/url_fetcher_response_writer.cc
@@ -102,8 +102,18 @@ int URLFetcherFileWriter::Write(IOBuffer* buffer,
 }
 
 int URLFetcherFileWriter::Finish(const CompletionCallback& callback) {
+  int result = file_stream_->Close(base::Bind(
+      &URLFetcherFileWriter::CloseComplete, base::Unretained(this), callback));

[mmenke, 2013/09/10 18:32:52]

The base::Unretained changes the safe usage model of the URLFetcherFileWriter. 
Previously, it could safely be deleted at any point.  You should use
weak_factory_.GetWeakPtr() here.

If you look at URLFetcherCore::CancelURLRequest and the calls into it from
URLFetchImpl, this seems to be a property that is relevant.  I don't see any
tests for this property, but may be worth adding.

[waffles, 2013/09/10 21:41:34]

Done.

+  if (result != ERR_IO_PENDING)
+    file_stream_.reset();
+  return result;
+}
+
+void URLFetcherFileWriter::CloseComplete(const CompletionCallback& callback,
+                                         int result) {
+  // Either we closed the file or we can't; either way destroy the file_stream.
   file_stream_.reset();
-  return OK;
+  callback.Run(result);
 }
 
 void URLFetcherFileWriter::DidWrite(const CompletionCallback& callback,