Avoid needless InstanceCounter.h inclusion.

third_party/WebKit/Source/wtf/RefCounted.h

Index: third_party/WebKit/Source/wtf/RefCounted.h
diff --git a/third_party/WebKit/Source/wtf/RefCounted.h b/third_party/WebKit/Source/wtf/RefCounted.h
index a4847efec651500b1c6776b8b3183b0ea5537421..a2820eaa4d421d41296fb052975af7e46b1fc2b6 100644
--- a/third_party/WebKit/Source/wtf/RefCounted.h
+++ b/third_party/WebKit/Source/wtf/RefCounted.h
@@ -23,10 +23,13 @@
 
 #include "wtf/Allocator.h"
 #include "wtf/Assertions.h"
-#include "wtf/InstanceCounter.h"
 #include "wtf/Noncopyable.h"
 #include "wtf/WTFExport.h"
 
+#if ENABLE(INSTANCE_COUNTER)
+#include "wtf/InstanceCounter.h"
+#endif
+
 #if DCHECK_IS_ON()
 #define CHECK_REF_COUNTED_LIFECYCLE 1
 #include "wtf/ThreadRestrictionVerifier.h"
@@ -152,7 +155,7 @@ class RefCounted : public RefCountedBase {
   }
 
  protected:
-#ifdef ENABLE_INSTANCE_COUNTER
+#if ENABLE(INSTANCE_COUNTER)
   RefCounted() { incrementInstanceCount<T>(static_cast<T*>(this)); }
 
   ~RefCounted() { decrementInstanceCount<T>(static_cast<T*>(this)); }