Decouple root visitors from object visitors.

src/builtins/builtins.h

Index: src/builtins/builtins.h
diff --git a/src/builtins/builtins.h b/src/builtins/builtins.h
index f895e2b138a0caacaaa179a77ef1b53214389f25..3f57b9bfb08c24c8b073ad44e87d52a36c641b0c 100644
--- a/src/builtins/builtins.h
+++ b/src/builtins/builtins.h
@@ -18,7 +18,7 @@ class Handle;
 class Isolate;
 
 // Forward declarations.
-class ObjectVisitor;
+class RootVisitor;
 enum class InterpreterPushArgsMode : unsigned;
 namespace compiler {
 class CodeAssemblerState;
@@ -31,7 +31,7 @@ class Builtins {
   void TearDown();
 
   // Garbage collection support.
-  void IterateBuiltins(ObjectVisitor* v);
+  void IterateBuiltins(RootVisitor* v);
 
   // Disassembler support.
   const char* Lookup(byte* pc);