Move prototype metadata from internal properties to prototype maps

src/transitions.cc

Index: src/transitions.cc
diff --git a/src/transitions.cc b/src/transitions.cc
index 2e65e387de74e05be69951495c5d3255ae04ba30..9fe9e8656447163d9fffcc2a5a8dce9400e2d3e7 100644
--- a/src/transitions.cc
+++ b/src/transitions.cc
@@ -316,6 +316,8 @@ void TransitionArray::SetNumberOfPrototypeTransitions(
 int TransitionArray::NumberOfTransitions(Object* raw_transitions) {
   if (CanStoreSimpleTransition(raw_transitions)) return 0;
   if (IsSimpleTransition(raw_transitions)) return 1;
+  // Prototype maps don't have transitions.
+  if (raw_transitions->IsPrototypeInfo()) return 0;
   DCHECK(IsFullTransitionArray(raw_transitions));
   return TransitionArray::cast(raw_transitions)->number_of_transitions();
 }