Add flag to tracing element kind transitions

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index 5507c98290df1319bd4b2d6c4050eaa8392c76ba..2633e638eddf4963bc7914a74172b6da8ca9ec06 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -173,6 +173,8 @@ enum ElementsKind {
 static const int kElementsKindCount =
     LAST_ELEMENTS_KIND - FIRST_ELEMENTS_KIND + 1;
 
+void PrintElementsKind(FILE* out, ElementsKind kind);
+
 // PropertyDetails captures type and attributes for a property.
 // They are used both in property dictionaries and instance descriptors.
 class PropertyDetails BASE_EMBEDDED {
@@ -857,6 +859,8 @@ class Object : public MaybeObject {
   HEAP_OBJECT_TYPE_LIST(IS_TYPE_FUNCTION_DECL)
 #undef IS_TYPE_FUNCTION_DECL
 
+  inline bool IsFixedArrayBase();
+
   // Returns true if this object is an instance of the specified
   // function template.
   inline bool IsInstanceOf(FunctionTemplateInfo* type);
@@ -1910,6 +1914,10 @@ class JSObject: public JSReceiver {
   void PrintElements(FILE* out);
 #endif
 
+  void PrintElementsTransition(
+      FILE* file, ElementsKind from_kind, FixedArrayBase* from_elements,
+      ElementsKind to_kind, FixedArrayBase* to_elements);
+
 #ifdef DEBUG
   // Structure for collecting spill information about JSObjects.
   class SpillInformation {