With >= 64 non-string instance types, I removed an optimization

src/objects-inl.h

Index: src/objects-inl.h
diff --git a/src/objects-inl.h b/src/objects-inl.h
index 0a5215cb405164a8df8044ac986fb5dda4288796..f215865e32481862351be89398dce7a94c03a6e8 100644
--- a/src/objects-inl.h
+++ b/src/objects-inl.h
@@ -221,9 +221,9 @@ bool Object::IsSpecFunction() {
 bool Object::IsInternalizedString() {
   if (!this->IsHeapObject()) return false;
   uint32_t type = HeapObject::cast(this)->map()->instance_type();
-  STATIC_ASSERT(kInternalizedTag != 0);
-  return (type & (kIsNotStringMask | kIsInternalizedMask)) ==
-      (kInternalizedTag | kStringTag);
+  STATIC_ASSERT(kNotInternalizedTag != 0);
+  return (type & (kIsNotStringMask | kIsNotInternalizedMask)) ==
+      (kStringTag | kInternalizedTag);
 }
 
 
@@ -319,9 +319,9 @@ StringShape::StringShape(InstanceType t)
 
 bool StringShape::IsInternalized() {
   ASSERT(valid());
-  STATIC_ASSERT(kInternalizedTag != 0);
-  return (type_ & (kIsNotStringMask | kIsInternalizedMask)) ==
-      (kInternalizedTag | kStringTag);
+  STATIC_ASSERT(kNotInternalizedTag != 0);
+  return (type_ & (kIsNotStringMask | kIsNotInternalizedMask)) ==
+      (kStringTag | kInternalizedTag);
 }