The check for internalized strings relied on the fact that we had less

src/objects-inl.h

Index: src/objects-inl.h
diff --git a/src/objects-inl.h b/src/objects-inl.h
index f3d2a661ae171b64fd658ad2fc35205a6bba37c6..5920679f6ab9b70360f151512257092ca81ffefc 100644
--- a/src/objects-inl.h
+++ b/src/objects-inl.h
@@ -221,12 +221,9 @@ bool Object::IsSpecFunction() {
 bool Object::IsInternalizedString() {
   if (!this->IsHeapObject()) return false;
   uint32_t type = HeapObject::cast(this)->map()->instance_type();
-  // Because the internalized tag is non-zero and no non-string types have the
-  // internalized bit set we can test for internalized strings with a very
-  // simple test operation.
   STATIC_ASSERT(kInternalizedTag != 0);
-  ASSERT(kNotStringTag + kIsInternalizedMask > LAST_TYPE);
-  return (type & kIsInternalizedMask) != 0;
+  return (type & (kIsNotStringMask | kIsInternalizedMask)) ==
+      (kInternalizedTag | kStringTag);
 }
 
 
@@ -323,7 +320,8 @@ StringShape::StringShape(InstanceType t)
 bool StringShape::IsInternalized() {
   ASSERT(valid());
   STATIC_ASSERT(kInternalizedTag != 0);
-  return (type_ & kIsInternalizedMask) != 0;
+  return (type_ & (kIsNotStringMask | kIsInternalizedMask)) ==
+      (kInternalizedTag | kStringTag);
 }
 
 
@@ -3388,15 +3386,13 @@ int Map::pre_allocated_property_fields() {
 int HeapObject::SizeFromMap(Map* map) {
   int instance_size = map->instance_size();
   if (instance_size != kVariableSizeSentinel) return instance_size;
-  // We can ignore the "internalized" bit because it is only set for strings
-  // and thus implies a string type.
-  int instance_type =
-      static_cast<int>(map->instance_type()) & ~kIsInternalizedMask;
   // Only inline the most frequent cases.
+  int instance_type = static_cast<int>(map->instance_type());
   if (instance_type == FIXED_ARRAY_TYPE) {
     return FixedArray::BodyDescriptor::SizeOf(map, this);
   }
-  if (instance_type == ASCII_STRING_TYPE) {
+  if (instance_type == ASCII_STRING_TYPE ||
+      instance_type == ASCII_INTERNALIZED_STRING_TYPE) {
     return SeqOneByteString::SizeFor(
         reinterpret_cast<SeqOneByteString*>(this)->length());
   }
@@ -3406,7 +3402,8 @@ int HeapObject::SizeFromMap(Map* map) {
   if (instance_type == FREE_SPACE_TYPE) {
     return reinterpret_cast<FreeSpace*>(this)->size();
   }
-  if (instance_type == STRING_TYPE) {
+  if (instance_type == STRING_TYPE ||
+      instance_type == INTERNALIZED_STRING_TYPE) {
     return SeqTwoByteString::SizeFor(
         reinterpret_cast<SeqTwoByteString*>(this)->length());
   }