Move Singleton and related structs to namespace base

extensions/browser/api/dns/host_resolver_wrapper.h

 // 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.
 
 #ifndef EXTENSIONS_BROWSER_API_DNS_HOST_RESOLVER_WRAPPER_H_
 #define EXTENSIONS_BROWSER_API_DNS_HOST_RESOLVER_WRAPPER_H_
 
 #include "base/memory/singleton.h"
 
 namespace content {
@@ skipping 22 matching lines @@
   // Given a pointer to a ResourceContext, returns its HostResolver if
   // SetHostResolverForTesting() hasn't been called, or else a
   // a substitute MockHostResolver to use instead.
   net::HostResolver* GetHostResolver(content::ResourceContext* context);
 
   // Sets the MockHostResolver to return in GetHostResolver().
   void SetHostResolverForTesting(net::HostResolver* mock_resolver);
 
  private:
   HostResolverWrapper();
-  friend struct DefaultSingletonTraits<HostResolverWrapper>;
+  friend struct base::DefaultSingletonTraits<HostResolverWrapper>;
 
   net::HostResolver* resolver_;
 
   DISALLOW_COPY_AND_ASSIGN(HostResolverWrapper);
 };
 
 }  // namespace extensions
 
 #endif  // EXTENSIONS_BROWSER_API_DNS_HOST_RESOLVER_WRAPPER_H_