URLFetcher won't call delegate until file is closed.

net/base/file_stream_context.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 "net/base/file_stream_context.h"
 
 #include "base/location.h"
 #include "base/message_loop/message_loop_proxy.h"
 #include "base/task_runner_util.h"
 #include "base/threading/thread_restrictions.h"
@@ skipping 87 matching lines @@
 
 void FileStream::Context::CloseSync() {
   DCHECK(!async_in_progress_);
   if (file_ != base::kInvalidPlatformFileValue) {
     base::ClosePlatformFile(file_);
     file_ = base::kInvalidPlatformFileValue;
     bound_net_log_.EndEvent(NetLog::TYPE_FILE_STREAM_OPEN);
   }
 }
 
+void FileStream::Context::CloseAsync(const CompletionCallback& callback) {
+  DCHECK(!async_in_progress_);
+  const bool posted = base::PostTaskAndReplyWithResult(
+      task_runner_.get(),
+      FROM_HERE,
+      base::Bind(&Context::CloseFileImpl, base::Unretained(this)),
+      base::Bind(&Context::ProcessAsyncResult,
+                 base::Unretained(this),
+                 IntToInt64(callback),
+                 FILE_ERROR_SOURCE_CLOSE));
+  DCHECK(posted);
+
+  async_in_progress_ = true;
+}
+
 void FileStream::Context::SeekAsync(Whence whence,
                                     int64 offset,
                                     const Int64CompletionCallback& callback) {
   DCHECK(!async_in_progress_);
 
   const bool posted = base::PostTaskAndReplyWithResult(
       task_runner_.get(),
       FROM_HERE,
       base::Bind(
           &Context::SeekFileImpl, base::Unretained(this), whence, offset),
@@ skipping 133 matching lines @@
   // operation is in progress.
   async_in_progress_ = false;
   if (orphaned_)
     CloseAndDelete();
   else
     callback.Run(result);
 }
 
 }  // namespace net