Disk cache: Remove all non essential synchronization from the cache destructor.

net/disk_cache/file.h

Index: net/disk_cache/file.h
===================================================================
--- net/disk_cache/file.h	(revision 126788)
+++ net/disk_cache/file.h	(working copy)
@@ -1,4 +1,4 @@
-// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// 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.
 
@@ -68,6 +68,9 @@
   // Blocks until |num_pending_io| IO operations complete.
   static void WaitForPendingIO(int* num_pending_io);
 
+  // Drops current pending operation without waiting for them to complete.

[gavinp, 2012/03/20 15:40:08]

Nit: // Drops current pending operations without waiting for them to complete.

+  static void DropPendingIO();
+
  protected:
   virtual ~File();