Using override keyword in ObjectVisitor class hierarchy.

src/heap/heap.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_HEAP_HEAP_H_
 #define V8_HEAP_HEAP_H_
 
 #include <cmath>
 #include <map>
 
@@ skipping 2411 matching lines @@
 };
 
 
 // Visitor class to verify interior pointers in spaces that do not contain
 // or care about intergenerational references. All heap object pointers have to
 // point into the heap to a location that has a map pointer at its first word.
 // Caveat: Heap::Contains is an approximation because it can return true for
 // objects in a heap space but above the allocation pointer.
 class VerifyPointersVisitor : public ObjectVisitor {
  public:
-  inline void VisitPointers(Object** start, Object** end);
+  inline void VisitPointers(Object** start, Object** end) override;
 };
 
 
 // Verify that all objects are Smis.
 class VerifySmisVisitor : public ObjectVisitor {
  public:
-  inline void VisitPointers(Object** start, Object** end);
+  inline void VisitPointers(Object** start, Object** end) override;
 };
 
 
 // Space iterator for iterating over all spaces of the heap.  Returns each space
 // in turn, and null when it is done.
 class AllSpaces BASE_EMBEDDED {
  public:
   explicit AllSpaces(Heap* heap) : heap_(heap), counter_(FIRST_SPACE) {}
   Space* next();
 
@@ skipping 240 matching lines @@
   PathTracer(Object* search_target, WhatToFind what_to_find,
              VisitMode visit_mode)
       : search_target_(search_target),
         found_target_(false),
         found_target_in_trace_(false),
         what_to_find_(what_to_find),
         visit_mode_(visit_mode),
         object_stack_(20),
         no_allocation() {}
 
-  virtual void VisitPointers(Object** start, Object** end);
+  void VisitPointers(Object** start, Object** end) override;
 
   void Reset();
   void TracePathFrom(Object** root);
 
   bool found() const { return found_target_; }
 
   static Object* const kAnyGlobalObject;
 
  protected:
   class MarkVisitor;
@@ skipping 13 matching lines @@
   DisallowHeapAllocation no_allocation;  // i.e. no gc allowed.
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(PathTracer);
 };
 #endif  // DEBUG
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_HEAP_HEAP_H_