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

net/disk_cache/sparse_control.cc

-// 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.
 
 #include "net/disk_cache/sparse_control.h"
 
 #include "base/bind.h"
 #include "base/format_macros.h"
 #include "base/logging.h"
 #include "base/message_loop.h"
 #include "base/string_util.h"
@@ skipping 423 matching lines @@
     // Keep using the same child or open another one?.
     if (key == child_->GetKey())
       return true;
     CloseChild();
   }
 
   // See if we are tracking this child.
   if (!ChildPresent())
     return ContinueWithoutChild(key);
 
+  if (!entry_->backend_)
+    return false;
+
   child_ = entry_->backend_->OpenEntryImpl(key);
   if (!child_)
     return ContinueWithoutChild(key);
 
   EntryImpl* child = static_cast<EntryImpl*>(child_);
   if (!(CHILD_ENTRY & child->GetEntryFlags()) ||
       child->GetDataSize(kSparseIndex) <
           static_cast<int>(sizeof(child_data_)))
     return KillChildAndContinue(key, false);
 
@@ skipping 52 matching lines @@
   return ContinueWithoutChild(key);
 }
 
 // We were not able to open this child; see what we can do.
 bool SparseControl::ContinueWithoutChild(const std::string& key) {
   if (kReadOperation == operation_)
     return false;
   if (kGetRangeOperation == operation_)
     return true;
 
+  if (!entry_->backend_)
+    return false;
+
   child_ = entry_->backend_->CreateEntryImpl(key);
   if (!child_) {
     child_ = NULL;
     result_ = net::ERR_CACHE_READ_FAILURE;
     return false;
   }
   // Write signature.
   InitChildData();
   return true;
 }
@@ skipping 336 matching lines @@
     net::CompletionCallback cb = abort_callbacks_[i];
     if (i == abort_callbacks_.size() - 1)
       abort_callbacks_.clear();
 
     entry_->Release();  // Don't touch object after this line.
     cb.Run(net::OK);
   }
 }
 
 }  // namespace disk_cache