Do not hide membership of implementation classes in dart:core.

runtime/vm/raw_object.h

Index: runtime/vm/raw_object.h
diff --git a/runtime/vm/raw_object.h b/runtime/vm/raw_object.h
index 3a978b340ca59f0f44bf4fb9e911447b5862b657..f329f566fbaf5b8e8a230fd26e6e1fdbc3c3c225 100644
--- a/runtime/vm/raw_object.h
+++ b/runtime/vm/raw_object.h
@@ -400,7 +400,6 @@ class RawObject {
   static bool IsTypedDataClassId(intptr_t index);
   static bool IsTypedDataViewClassId(intptr_t index);
   static bool IsExternalTypedDataClassId(intptr_t index);
-  static bool IsImplementationClassId(intptr_t index);
   static bool IsInternalVMdefinedClassId(intptr_t index);
 
   static intptr_t NumberOfTypedDataClasses();
@@ -1703,13 +1702,6 @@ inline bool RawObject::IsExternalTypedDataClassId(intptr_t index) {
 }
 
 
-inline bool RawObject::IsImplementationClassId(intptr_t index) {
-  return IsBuiltinListClassId(index) ||
-      IsStringClassId(index) ||
-      IsNumberClassId(index);
-}
-
-
 inline bool RawObject::IsInternalVMdefinedClassId(intptr_t index) {
   return ((index < kNumPredefinedCids) &&
           !RawObject::IsTypedDataViewClassId(index));