URLFetcher won't call delegate until file is closed.

net/base/file_stream_context.h

 // 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.
 
 // This file defines FileStream::Context class.
 // The general design of FileStream is as follows: file_stream.h defines
 // FileStream class which basically is just an "wrapper" not containing any
 // specific implementation details. It re-routes all its method calls to
 // the instance of FileStream::Context (FileStream holds a scoped_ptr to
 // FileStream::Context instance). Context was extracted into a different class
@@ skipping 91 matching lines @@
   // not closed yet.
   void Orphan();
 
   void OpenAsync(const base::FilePath& path,
                  int open_flags,
                  const CompletionCallback& callback);
   int OpenSync(const base::FilePath& path, int open_flags);
 
   void CloseSync();
 
+  void CloseAsync(const CompletionCallback& callback);
+
   void SeekAsync(Whence whence,
                  int64 offset,
                  const Int64CompletionCallback& callback);
   int64 SeekSync(Whence whence, int64 offset);
 
   void FlushAsync(const CompletionCallback& callback);
   int FlushSync();
 
  private:
   ////////////////////////////////////////////////////////////////////////////
@@ skipping 62 matching lines @@
   // Platform-dependent methods implemented in
   // file_stream_context_{win,posix}.cc.
   ////////////////////////////////////////////////////////////////////////////
 
   // Adjusts the position from where the data is read.
   IOResult SeekFileImpl(Whence whence, int64 offset);
 
   // Flushes all data written to the stream.
   IOResult FlushFileImpl();
 
+  // Closes the file.
+  IOResult CloseFileImpl();
+
 #if defined(OS_WIN)
   void IOCompletionIsPending(const CompletionCallback& callback, IOBuffer* buf);
 
   // Implementation of MessageLoopForIO::IOHandler.
   virtual void OnIOCompleted(base::MessageLoopForIO::IOContext* context,
                              DWORD bytes_read,
                              DWORD error) OVERRIDE;
 #elif defined(OS_POSIX)
   // ReadFileImpl() is a simple wrapper around read() that handles EINTR
   // signals and calls RecordAndMapError() to map errno to net error codes.
@@ skipping 19 matching lines @@
   FileErrorSource error_source_;
 #endif
 
   DISALLOW_COPY_AND_ASSIGN(Context);
 };
 
 }  // namespace net
 
 #endif  // NET_BASE_FILE_STREAM_CONTEXT_H_