Improve generalization / migration tracing.

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index f800c5d580eace363c14b94ac947af8cec798fc7..96b4011664bef5255601b653a0a664e1a7367551 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -2672,6 +2672,8 @@ class JSObject: public JSReceiver {
       FILE* file, ElementsKind from_kind, FixedArrayBase* from_elements,
       ElementsKind to_kind, FixedArrayBase* to_elements);
 
+  void PrintInstanceMigration(FILE* file, Map* original_map, Map* new_map);
+
 #ifdef DEBUG
   // Structure for collecting spill information about JSObjects.
   class SpillInformation {
@@ -5623,6 +5625,17 @@ class Map: public HeapObject {
       Representation representation);
   MUST_USE_RESULT MaybeObject* CopyGeneralizeAllRepresentations();
 
+  void PrintGeneralization(FILE* file,
+                           int modify_index,
+                           int split,
+                           int descriptors,
+                           Representation old_representation,
+                           Representation new_representation);
+
+  // Returns the constructor name (the name (possibly, inferred name) of the
+  // function that was used to instantiate the object).
+  String* constructor_name();
+
   // Tells whether the map is attached to SharedFunctionInfo
   // (for inobject slack tracking).
   inline void set_attached_to_shared_function_info(bool value);