components: Cleanup class/struct fwd declarations

components/variations/variations_associated_data.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 COMPONENTS_VARIATIONS_VARIATIONS_ASSOCIATED_DATA_H_
 #define COMPONENTS_VARIATIONS_VARIATIONS_ASSOCIATED_DATA_H_
 
 #include <map>
 #include <memory>
 #include <string>
@@ skipping 32 matching lines @@
 //   // use |id|
 // }
 
 namespace base {
 struct Feature;
 }
 
 namespace variations {
 
 typedef int VariationID;
-class VariationsHttpHeaderProvider;
 
 const VariationID EMPTY_ID = 0;
 
 // A key into the Associate/Get methods for VariationIDs. This is used to create
 // separate ID associations for separate parties interested in VariationIDs.
 enum IDCollectionKey {
   // This collection is used by Google web properties, transmitted through the
   // X-Client-Data header.
   GOOGLE_WEB_PROPERTIES,
   // This collection is used by Google web properties for IDs that trigger
@@ skipping 129 matching lines @@
 void ClearAllVariationIDs();
 
 // Clears all of the associated params.
 void ClearAllVariationParams();
 
 }  // namespace testing
 
 }  // namespace variations
 
 #endif  // COMPONENTS_VARIATIONS_VARIATIONS_ASSOCIATED_DATA_H_