Fix --serialization-statistics.

R=jgruber@chromium.org

Bug: v8:7227, v8:7228
Change-Id: I2c567a6bf4a3d1128559ae440182bd14fb78d005
Reviewed-on: https://chromium-review.googlesource.com/832462
Commit-Queue: Yang Guo <yangguo@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#50198}

src/snapshot/serializer.h

@@ -252,7 +252,7 @@ class Serializer : public SerializerDeserializer {
   AllocatorT allocator_;
 
 #ifdef OBJECT_PRINT
-  static const int kInstanceTypes = 256;
+  static const int kInstanceTypes = LAST_TYPE + 1;
   int* instance_type_count_;
   size_t* instance_type_size_;
 #endif  // OBJECT_PRINT