Move Singleton and related structs to namespace base

content/browser/signed_certificate_timestamp_store_impl.h

 // Copyright 2013 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 CONTENT_BROWSER_SIGNED_CERTIFICATE_TIMESTAMP_STORE_IMPL_H_
 #define CONTENT_BROWSER_SIGNED_CERTIFICATE_TIMESTAMP_STORE_IMPL_H_
 
 #include "content/browser/renderer_data_memoizing_store.h"
 #include "content/public/browser/signed_certificate_timestamp_store.h"
 #include "net/cert/signed_certificate_timestamp.h"
 
+namespace base {
 template <typename T> struct DefaultSingletonTraits;
+}
 
 namespace content {
 
 class SignedCertificateTimestampStoreImpl
     : public SignedCertificateTimestampStore {
  public:
   // Returns the singleton instance of the SignedCertificateTimestampStore.
   static SignedCertificateTimestampStoreImpl* GetInstance();
 
   // SignedCertificateTimestampStore implementation:
   int Store(net::ct::SignedCertificateTimestamp* sct,
             int render_process_host_id) override;
   bool Retrieve(
       int sct_id,
       scoped_refptr<net::ct::SignedCertificateTimestamp>* sct) override;
 
  private:
-  friend struct DefaultSingletonTraits<SignedCertificateTimestampStoreImpl>;
+  friend struct base::DefaultSingletonTraits<
+      SignedCertificateTimestampStoreImpl>;
 
   SignedCertificateTimestampStoreImpl();
   ~SignedCertificateTimestampStoreImpl() override;
 
   RendererDataMemoizingStore<net::ct::SignedCertificateTimestamp> store_;
 
   DISALLOW_COPY_AND_ASSIGN(SignedCertificateTimestampStoreImpl);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_SIGNED_CERTIFICATE_TIMESTAMP_STORE_IMPL_H_