Decouple root visitors from object visitors.

src/heap/scavenger.cc

Index: src/heap/scavenger.cc
diff --git a/src/heap/scavenger.cc b/src/heap/scavenger.cc
index 7a8e55fd19320beb3dd0efbfc55bd794a1029bbf..72f8c1b786fbd1e4fc134e410a366c58525bd7f1 100644
--- a/src/heap/scavenger.cc
+++ b/src/heap/scavenger.cc
@@ -460,17 +460,24 @@ void Scavenger::SelectScavengingVisitorsTable() {
 
 Isolate* Scavenger::isolate() { return heap()->isolate(); }
 
+void RootScavengeVisitor::VisitPointer(Object** p) { ScavengePointer(p); }
 
-void ScavengeVisitor::VisitPointer(Object** p) { ScavengePointer(p); }
+void RootScavengeVisitor::VisitPointers(Object** start, Object** end) {
+  // Copy all HeapObject pointers in [start, end)
+  for (Object** p = start; p < end; p++) ScavengePointer(p);
+}
 
+void RootScavengeVisitor::VisitRootPointer(Root root, Object** p) {
+  ScavengePointer(p);
+}
 
-void ScavengeVisitor::VisitPointers(Object** start, Object** end) {
+void RootScavengeVisitor::VisitRootPointers(Root root, Object** start,
+                                            Object** end) {
   // Copy all HeapObject pointers in [start, end)
   for (Object** p = start; p < end; p++) ScavengePointer(p);
 }
 
-
-void ScavengeVisitor::ScavengePointer(Object** p) {
+void RootScavengeVisitor::ScavengePointer(Object** p) {
   Object* object = *p;
   if (!heap_->InNewSpace(object)) return;