Promoting elements transitions to their own field.

src/heap.cc

Index: src/heap.cc
diff --git a/src/heap.cc b/src/heap.cc
index a224e2bf50f137873e073b78d319ea48357f4ea9..7ea8f21a5075c6219b4268a47918f4fd16f7bb34 100644
--- a/src/heap.cc
+++ b/src/heap.cc
@@ -3666,7 +3666,8 @@ MaybeObject* Heap::AllocateFunctionPrototype(JSFunction* function) {
   Map* new_map;
   ASSERT(object_function->has_initial_map());
   { MaybeObject* maybe_map =
-        object_function->initial_map()->CopyDropTransitions();
+        object_function->initial_map()->CopyDropTransitions(
+            DescriptorArray::MAY_BE_SHARED);
     if (!maybe_map->To<Map>(&new_map)) return maybe_map;
   }
   Object* prototype;
@@ -3814,7 +3815,8 @@ MaybeObject* Heap::AllocateInitialMap(JSFunction* fun) {
       fun->shared()->ForbidInlineConstructor();
     } else {
       DescriptorArray* descriptors;
-      { MaybeObject* maybe_descriptors_obj = DescriptorArray::Allocate(count);
+      { MaybeObject* maybe_descriptors_obj =
+            DescriptorArray::Allocate(count, DescriptorArray::MAY_BE_SHARED);
         if (!maybe_descriptors_obj->To<DescriptorArray>(&descriptors)) {
           return maybe_descriptors_obj;
         }