Disallow UI/IO thread blocking on any other thread.

net/base/file_stream_win.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.h"
 
 #include <windows.h>
 
 #include "base/file_path.h"
 #include "base/logging.h"
@@ skipping 709 matching lines @@
   ResetOnIOComplete();
   callback.Run(*result);
 }
 
 void FileStreamWin::ResetOnIOComplete() {
   on_io_complete_.reset();
   weak_ptr_factory_.InvalidateWeakPtrs();
 }
 
 void FileStreamWin::WaitForIOCompletion() {
+  base::ThreadRestrictions::ScopedAllowWait allow_wait;
   if (on_io_complete_.get()) {
     on_io_complete_->Wait();
     on_io_complete_.reset();
   }
 }
 
 }  // namespace net