URLFetcher won't call delegate until file is closed.

net/url_request/url_fetcher_response_writer.cc

 // Copyright (c) 2013 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 "net/url_request/url_fetcher_response_writer.h"
 
 #include "base/file_util.h"
 #include "base/location.h"
 #include "base/task_runner.h"
 #include "base/task_runner_util.h"
@@ skipping 84 matching lines @@
                                               weak_factory_.GetWeakPtr(),
                                               callback));
   if (result < 0 && result != ERR_IO_PENDING) {
     error_code_ = result;
     CloseAndDeleteFile();
   }
   return result;
 }
 
 int URLFetcherFileWriter::Finish(const CompletionCallback& callback) {
+  int result = file_stream_->Close(base::Bind(
+      &URLFetcherFileWriter::CloseComplete,
+      weak_factory_.GetWeakPtr(), callback));
+  if (result != ERR_IO_PENDING)
+    file_stream_.reset();
+  return result;
+}
+
+void URLFetcherFileWriter::CloseComplete(const CompletionCallback& callback,
+                                         int result) {
+  // Destroy |file_stream_| whether or not the close succeeded.
   file_stream_.reset();
-  return OK;
+  callback.Run(result);
 }
 
 void URLFetcherFileWriter::DidWrite(const CompletionCallback& callback,
                                     int result) {
   if (result < 0) {
     error_code_ = result;
     CloseAndDeleteFile();
   }
   callback.Run(result);
 }
@@ skipping 45 matching lines @@
     total_bytes_written_ = 0;
     owns_file_ = true;
   } else {
     error_code_ = result;
     CloseAndDeleteFile();
   }
   callback.Run(result);
 }
 
 }  // namespace net