Update {virtual,override} to follow C++11 style in net.

net/disk_cache/blockfile/backend_impl_v3.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/disk_cache/blockfile/backend_impl_v3.h"
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "base/files/file_path.h"
 #include "base/files/file_util.h"
@@ skipping 649 matching lines @@
     SyncEndEnumeration(iter);  // Dooming the entry invalidates the iterator.
   }
 }
 
 class BackendImplV3::IteratorImpl : public Backend::Iterator {
  public:
   explicit IteratorImpl(base::WeakPtr<InFlightBackendIO> background_queue)
       : background_queue_(background_queue), data_(NULL) {
   }
 
-  virtual int OpenNextEntry(Entry** next_entry,
-                            const net::CompletionCallback& callback) override {
+  int OpenNextEntry(Entry** next_entry,
+                    const net::CompletionCallback& callback) override {
     if (!background_queue_)
       return net::ERR_FAILED;
     background_queue_->OpenNextEntry(&data_, next_entry, callback);
     return net::ERR_IO_PENDING;
   }
 
  private:
   const base::WeakPtr<InFlightBackendIO> background_queue_;
   void* data_;
 };
@@ skipping 844 matching lines @@
 }
 
 void BackendImplV3::OnExternalCacheHit(const std::string& key) {
   NOTIMPLEMENTED();
 }
 
 void BackendImplV3::CleanupCache() {
 }
 
 }  // namespace disk_cache