Decouple root visitors from object visitors.

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index d5461a7fd49fce8b4ab6d930171409a94fa50012..f8e0da0b5de4d0c97cbbae8363e6bbee9f96ad48 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -951,6 +951,7 @@ class ObjectHashTable;
 class ObjectVisitor;
 class PropertyCell;
 class PropertyDescriptor;
+class RootVisitor;
 class SafepointEntry;
 class SharedFunctionInfo;
 class StringStream;
@@ -8709,16 +8710,16 @@ class Relocatable BASE_EMBEDDED {
  public:
   explicit inline Relocatable(Isolate* isolate);
   inline virtual ~Relocatable();
-  virtual void IterateInstance(ObjectVisitor* v) { }
+  virtual void IterateInstance(RootVisitor* v) {}
   virtual void PostGarbageCollection() { }
 
   static void PostGarbageCollectionProcessing(Isolate* isolate);
   static int ArchiveSpacePerThread();
   static char* ArchiveState(Isolate* isolate, char* to);
   static char* RestoreState(Isolate* isolate, char* from);
-  static void Iterate(Isolate* isolate, ObjectVisitor* v);
-  static void Iterate(ObjectVisitor* v, Relocatable* top);
-  static char* Iterate(ObjectVisitor* v, char* t);
+  static void Iterate(Isolate* isolate, RootVisitor* v);
+  static void Iterate(RootVisitor* v, Relocatable* top);
+  static char* Iterate(RootVisitor* v, char* t);
 
  private:
   Isolate* isolate_;
@@ -10141,40 +10142,9 @@ class StackFrameInfo : public Struct {
   DISALLOW_IMPLICIT_CONSTRUCTORS(StackFrameInfo);
 };
 
-#define VISITOR_SYNCHRONIZATION_TAGS_LIST(V)                               \
-  V(kStringTable, "string_table", "(Internalized strings)")                \
-  V(kExternalStringsTable, "external_strings_table", "(External strings)") \
-  V(kStrongRootList, "strong_root_list", "(Strong roots)")                 \
-  V(kSmiRootList, "smi_root_list", "(Smi roots)")                          \
-  V(kBootstrapper, "bootstrapper", "(Bootstrapper)")                       \
-  V(kTop, "top", "(Isolate)")                                              \
-  V(kRelocatable, "relocatable", "(Relocatable)")                          \
-  V(kDebug, "debug", "(Debugger)")                                         \
-  V(kCompilationCache, "compilationcache", "(Compilation cache)")          \
-  V(kHandleScope, "handlescope", "(Handle scope)")                         \
-  V(kDispatchTable, "dispatchtable", "(Dispatch table)")                   \
-  V(kBuiltins, "builtins", "(Builtins)")                                   \
-  V(kGlobalHandles, "globalhandles", "(Global handles)")                   \
-  V(kEternalHandles, "eternalhandles", "(Eternal handles)")                \
-  V(kThreadManager, "threadmanager", "(Thread manager)")                   \
-  V(kStrongRoots, "strong roots", "(Strong roots)")                        \
-  V(kExtensions, "Extensions", "(Extensions)")
-
-class VisitorSynchronization : public AllStatic {
- public:
-#define DECLARE_ENUM(enum_item, ignore1, ignore2) enum_item,
-  enum SyncTag {
-    VISITOR_SYNCHRONIZATION_TAGS_LIST(DECLARE_ENUM)
-    kNumberOfSyncTags
-  };
-#undef DECLARE_ENUM
-
-  static const char* const kTags[kNumberOfSyncTags];
-  static const char* const kTagNames[kNumberOfSyncTags];
-};
-
 // Abstract base class for visiting, and optionally modifying, the
 // pointers contained in Objects. Used in GC and serialization/deserialization.
+// TODO(ulan): move to src/visitors.h
 class ObjectVisitor BASE_EMBEDDED {
  public:
   virtual ~ObjectVisitor() {}
@@ -10222,11 +10192,6 @@ class ObjectVisitor BASE_EMBEDDED {
 
   // Visits an (encoded) internal reference.
   virtual void VisitInternalReference(RelocInfo* rinfo) {}
-
-  // Intended for serialization/deserialization checking: insert, or
-  // check for the presence of, a tag at this position in the stream.
-  // Also used for marking up GC roots in heap snapshots.
-  virtual void Synchronize(VisitorSynchronization::SyncTag tag) {}
 };