Remove trace() methods for stack-only classes.

third_party/WebKit/Source/core/css/resolver/CSSVariableResolver.cpp

 // Copyright 2015 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 "core/css/resolver/CSSVariableResolver.h"
 
 #include "core/CSSPropertyNames.h"
 #include "core/CSSValueKeywords.h"
 #include "core/StyleBuilderFunctions.h"
 #include "core/StylePropertyShorthand.h"
@@ skipping 315 matching lines @@
       }
     }
   }
 }
 
 CSSVariableResolver::CSSVariableResolver(const StyleResolverState& state)
     : m_inheritedVariables(state.style()->inheritedVariables()),
       m_nonInheritedVariables(state.style()->nonInheritedVariables()),
       m_registry(state.document().propertyRegistry()) {}
 
-DEFINE_TRACE(CSSVariableResolver) {
-  visitor->trace(m_registry);
-}
-
 }  // namespace blink