Avoiding IO completion callback during the closing

net/base/file_stream_posix.cc

Index: net/base/file_stream_posix.cc
===================================================================
--- net/base/file_stream_posix.cc	(revision 16872)
+++ net/base/file_stream_posix.cc	(working copy)
@@ -200,6 +200,8 @@
   int result_;
   CancelableCallbackTask* message_loop_task_;
 
+  bool is_closing_;
+
   DISALLOW_COPY_AND_ASSIGN(AsyncContext);
 };
 
@@ -209,9 +211,11 @@
       background_io_completed_callback_(
           this, &AsyncContext::OnBackgroundIOCompleted),
       background_io_completed_(true, false),
-      message_loop_task_(NULL) {}
+      message_loop_task_(NULL),
+      is_closing_(false) {}
 
 FileStream::AsyncContext::~AsyncContext() {
+  is_closing_ = true;
   if (callback_) {
     // If |callback_| is non-NULL, that implies either the worker thread is
     // still running the IO task, or the completion callback is queued up on the
@@ -271,6 +275,11 @@
   message_loop_task_->Cancel();
   message_loop_task_ = NULL;
 
+  if (is_closing_) {
+    callback_ = NULL;
+    return;
+  }
+
   DCHECK(callback_);
   CompletionCallback* temp = NULL;
   std::swap(temp, callback_);