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

net/disk_cache/sparse_control.h

Index: net/disk_cache/sparse_control.h
===================================================================
--- net/disk_cache/sparse_control.h	(revision 126788)
+++ net/disk_cache/sparse_control.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.
 
@@ -32,6 +32,8 @@
 // used directly for sparse operations (the entry passed in to the constructor).
 class SparseControl {
  public:
+  typedef net::CompletionCallback CompletionCallback;
+
   // The operation to perform.
   enum SparseOperation {
     kNoOperation,
@@ -59,7 +61,7 @@
   // WriteSparseData for details about the arguments. The return value is the
   // number of bytes read or written, or a net error code.
   int StartIO(SparseOperation op, int64 offset, net::IOBuffer* buf,
-              int buf_len, const net::CompletionCallback& callback);
+              int buf_len, const CompletionCallback& callback);
 
   // Implements Entry::GetAvailableRange().
   int GetAvailableRange(int64 offset, int len, int64* start);
@@ -70,7 +72,7 @@
   // Returns OK if the entry can be used for new IO or ERR_IO_PENDING if we are
   // busy. If the entry is busy, we'll invoke the callback when we are ready
   // again. See disk_cache::Entry::ReadyToUse() for more info.
-  int ReadyToUse(const net::CompletionCallback& completion_callback);
+  int ReadyToUse(const CompletionCallback& completion_callback);
 
   // Deletes the children entries of |entry|.
   static void DeleteChildren(EntryImpl* entry);
@@ -159,8 +161,8 @@
   SparseData child_data_;  // Parent and allocation map of child_.
   Bitmap child_map_;  // The allocation map as a bitmap.
 
-  net::CompletionCallback user_callback_;
-  std::vector<net::CompletionCallback> abort_callbacks_;
+  CompletionCallback user_callback_;
+  std::vector<CompletionCallback> abort_callbacks_;
   int64 offset_;  // Current sparse offset.
   scoped_refptr<net::DrainableIOBuffer> user_buf_;
   int buf_len_;  // Bytes to read or write.