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 506c314a5ad3759b041f8a8ffa265178e0ee3254..f43e485f4e97ce4f1117abfe1ed26c3a7c690886 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();
@@ -1701,13 +1700,6 @@ 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));