Move Singleton and related structs to namespace base

components/variations/net/variations_http_header_provider.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 COMPONENTS_VARIATIONS_NET_VARIATIONS_HTTP_HEADER_PROVIDER_H_
 #define COMPONENTS_VARIATIONS_NET_VARIATIONS_HTTP_HEADER_PROVIDER_H_
 
 #include <set>
 #include <string>
 #include <vector>
 
 #include "base/basictypes.h"
 #include "base/gtest_prod_util.h"
 #include "base/metrics/field_trial.h"
 #include "base/synchronization/lock.h"
 #include "components/metrics/metrics_service.h"
 #include "components/variations/variations_associated_data.h"
 
 namespace content {
 class ResourceContext;
 }
 
 namespace net {
 class HttpRequestHeaders;
 }
 
 class GURL;
 
+namespace base {
 template <typename T> struct DefaultSingletonTraits;
+}
 
 namespace variations {
 
 // A helper class for maintaining client experiments and metrics state
 // transmitted in custom HTTP request headers.
 // This class is a thread-safe singleton.
 class VariationsHttpHeaderProvider : public base::FieldTrialList::Observer,
                                      public metrics::SyntheticTrialObserver {
  public:
   static VariationsHttpHeaderProvider* GetInstance();
@@ skipping 14 matching lines @@
   // with "t" it will be treated as a trigger experiment id.
   bool SetDefaultVariationIds(const std::string& variation_ids);
 
   // Returns the HTTP header names which are added in this class.
   std::set<std::string> GetVariationHeaderNames() const;
 
   // Resets any cached state for tests.
   void ResetForTesting();
 
  private:
-  friend struct DefaultSingletonTraits<VariationsHttpHeaderProvider>;
+  friend struct base::DefaultSingletonTraits<VariationsHttpHeaderProvider>;
 
   FRIEND_TEST_ALL_PREFIXES(VariationsHttpHeaderProviderTest,
                            ShouldAppendHeaders);
   FRIEND_TEST_ALL_PREFIXES(VariationsHttpHeaderProviderTest,
                            SetDefaultVariationIds_Valid);
   FRIEND_TEST_ALL_PREFIXES(VariationsHttpHeaderProviderTest,
                            SetDefaultVariationIds_Invalid);
   FRIEND_TEST_ALL_PREFIXES(VariationsHttpHeaderProviderTest,
                            OnFieldTrialGroupFinalized);
 
@@ skipping 44 matching lines @@
   std::set<VariationID> synthetic_variation_ids_set_;
 
   std::string variation_ids_header_;
 
   DISALLOW_COPY_AND_ASSIGN(VariationsHttpHeaderProvider);
 };
 
 }  // namespace variations
 
 #endif  // COMPONENTS_VARIATIONS_NET_VARIATIONS_HTTP_HEADER_PROVIDER_H_