Warn about extractTypeNameFromFunctionName usage

Source/wtf/InstanceCounter.h

Index: Source/wtf/InstanceCounter.h
diff --git a/Source/wtf/InstanceCounter.h b/Source/wtf/InstanceCounter.h
index 7b359ab374c6c6813d83cc341c62c06bcf33c3a4..602de6559fdf87fa0c76a4b9b4f6b43bd5e9e49c 100644
--- a/Source/wtf/InstanceCounter.h
+++ b/Source/wtf/InstanceCounter.h
@@ -34,6 +34,10 @@ namespace WTF {
 class String;
 WTF_EXPORT String dumpRefCountedInstanceCounts();
 
+// Warning: Using extractTypeNameFromFunctionName bloats binary size.
+// This function should be only used for debug and profiling purposes,
+// and should be never enabled on release builds.
+// TODO(kouhei): Move this inside #if when all dependencies are removed.
 WTF_EXPORT String extractTypeNameFromFunctionName(const char* funcName);
 
 template<typename T>