Remove unused methods.

src/mark-compact.cc

Index: src/mark-compact.cc
diff --git a/src/mark-compact.cc b/src/mark-compact.cc
index 06df3fcb2dfbe18e56cf08af6205d9238436d175..fc1ab92704f46a66326d74b953237494331206de 100644
--- a/src/mark-compact.cc
+++ b/src/mark-compact.cc
@@ -869,18 +869,6 @@ class MarkingVisitor : public ObjectVisitor {
     StaticMarkingVisitor::VisitPointers(heap_, start, end);
   }
 
-  void VisitCodeTarget(Heap* heap, RelocInfo* rinfo) {
-    StaticMarkingVisitor::VisitCodeTarget(heap, rinfo);
-  }
-
-  void VisitGlobalPropertyCell(Heap* heap, RelocInfo* rinfo) {
-    StaticMarkingVisitor::VisitGlobalPropertyCell(heap, rinfo);
-  }
-
-  void VisitDebugTarget(Heap* heap, RelocInfo* rinfo) {
-    StaticMarkingVisitor::VisitDebugTarget(heap, rinfo);
-  }
-
  private:
   Heap* heap_;
 };