Reduce platform/heap/ wtf includes.

Source/platform/heap/Visitor.h

Index: Source/platform/heap/Visitor.h
diff --git a/Source/platform/heap/Visitor.h b/Source/platform/heap/Visitor.h
index c918e95976fc1c1147cd5d8e9281508b6c242b9d..adbdbc564a49569d2e1b0cec208cfbcfef12c3a7 100644
--- a/Source/platform/heap/Visitor.h
+++ b/Source/platform/heap/Visitor.h
@@ -40,21 +40,12 @@
 #include "wtf/Forward.h"
 #include "wtf/HashMap.h"
 #include "wtf/HashTraits.h"
-#include "wtf/InstanceCounter.h"
-#include "wtf/OwnPtr.h"
-#include "wtf/RefPtr.h"
 #include "wtf/TypeTraits.h"
-#include "wtf/WeakPtr.h"
 #if ENABLE(GC_PROFILING)
+#include "wtf/InstanceCounter.h"
 #include "wtf/text/WTFString.h"
 #endif
 
-#if ENABLE(ASSERT)
-#define DEBUG_ONLY(x) x
-#else
-#define DEBUG_ONLY(x)
-#endif
-
 namespace blink {
 
 template<typename T> class GarbageCollected;
@@ -107,10 +98,8 @@ struct GCInfo {
 
 #if ENABLE(ASSERT)
 PLATFORM_EXPORT void assertObjectHasGCInfo(const void*, size_t gcInfoIndex);
-
 #endif
 
-
 // The FinalizerTraitImpl specifies how to finalize objects. Object
 // that inherit from GarbageCollectedFinalized are finalized by
 // calling their 'finalize' method which by default will call the
@@ -1020,6 +1009,6 @@ struct GCInfoTrait {
     }
 };
 
-}
+} // namespace blink
 
-#endif
+#endif // Visitor_h