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

chrome/browser/local_discovery/service_discovery_client_mdns.cc

 // Copyright 2014 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 "chrome/browser/local_discovery/service_discovery_client_mdns.h"
 
 #include "base/memory/scoped_vector.h"
 #include "base/metrics/histogram.h"
 #include "chrome/common/local_discovery/service_discovery_client_impl.h"
 #include "content/public/browser/browser_thread.h"
@@ skipping 127 matching lines @@
 
 template<class T>
 class ProxyBase : public ServiceDiscoveryClientMdns::Proxy, public T {
  public:
   typedef ProxyBase<T> Base;
 
   explicit ProxyBase(ServiceDiscoveryClientMdns* client)
       : Proxy(client) {
   }
 
-  virtual ~ProxyBase() {
+  ~ProxyBase() override {
     DeleteOnMdnsThread(implementation_.release());
   }
 
-  virtual bool IsValid() override {
+  bool IsValid() override {
     return !!implementation();
   }
 
-  virtual void OnMdnsDestroy() override {
+  void OnMdnsDestroy() override {
     DeleteOnMdnsThread(implementation_.release());
   };
 
  protected:
   void set_implementation(scoped_ptr<T> implementation) {
     implementation_ = implementation.Pass();
   }
 
   T* implementation()  const {
     return implementation_.get();
@@ skipping 265 matching lines @@
   OnBeforeMdnsDestroy();
   // After calling |Proxy::OnMdnsDestroy| all references to client_ and mdns_
   // should be destroyed.
   if (client_)
     mdns_runner_->DeleteSoon(FROM_HERE, client_.release());
   if (mdns_)
     mdns_runner_->DeleteSoon(FROM_HERE, mdns_.release());
 }
 
 }  // namespace local_discovery